# 100 leading professional services firms in California

Tamtam tracks 880 professional services firms headquartered in California. This list ranks the 100 largest by number of employees on LinkedIn, led by Concentrix, Allied Universal and GlobalLogic. Their median headcount is 2,449. Half of them were founded in 1993 or later. The most common headquarters are San Francisco (20), Los Angeles (16) and San Jose (8).

The largest professional services firms in California are predominantly large groups with extensive workforces. These companies cover a wide array of specialized services, from IT and software development to civil engineering and financial services. For instance, Concentrix provides customer experience solutions, while Allied Universal specializes in security and facility services. Tetra Tech offers consulting and engineering for environmental and infrastructure projects, and Robert Half connects professionals with companies for various placements.

The data reveals a strong presence of IT services and staffing firms among the largest employers. Several companies, such as Concentrix, GlobalLogic, and Xoriant, focus on technology and digital solutions. Furthermore, a notable cluster of headquarters is observed in the Bay Area, including cities like San Francisco, Santa Clara, and Menlo Park, indicating a concentration of these large professional services operations in Northern California.

🇺🇸 California · 100 companies · Updated Nov 11, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [Concentrix](https://www.tamtam.ai/c/concentrix) (concentrix.com)<br>Provides customer experience solutions and technology, improving business performance for global brands across various industries, creating better business outcomes. | IT Services and IT Consulting | 🇺🇸 Newark | 218,681 | 1983 |
| 2 | [Allied Universal](https://www.tamtam.ai/c/allied-universal) (aus.com)<br>Provides tailored security and facility services using smart technology, supporting diverse sectors with local leadership and community presence. | Professional Services | 🇺🇸 Irvine | 104,797 |  |
| 3 | [GlobalLogic](https://www.tamtam.ai/c/globallogic) (globallogic.com)<br>A global product development services leader, combining software engineering expertise and industry experience to help customers design and deliver next-generation products and digital experiences | Software Development | 🇺🇸 Santa Clara | 35,494 |  |
| 4 | [Globant](https://www.tamtam.ai/c/globant) (globant.com)<br>A digitally native company specializing in helping organizations innovate and unleash potential, with a focus on diversity, inclusion, and cybersecurity | IT Services and IT Consulting | 🇺🇸 San Francisco | 28,419 |  |
| 5 | [Tetra Tech](https://www.tamtam.ai/c/tetra-tech) (tetratech.com)<br>A global provider of consulting and engineering services, specializing in innovative technical solutions for water, environment, infrastructure, energy, and international development projects | Civil Engineering | 🇺🇸 Pasadena | 27,460 |  |
| 6 | [Robert Half](https://www.tamtam.ai/c/robert-half) (roberthalf.com)<br>Connecting skilled professionals with companies through contract, temporary, and permanent placements in finance, technology, marketing, legal, and administrative sectors. | Staffing and Recruiting | 🇺🇸 Menlo Park | 26,429 | 1948 |
| 7 | [Korn Ferry](https://www.tamtam.ai/c/korn-ferry) (kornferry.com)<br>It is a global consulting firm specializing in organizational design, hiring, workforce motivation, and professional development for career advancement. | Business Consulting and Services | 🇺🇸 Los Angeles | 21,328 |  |
| 8 | [Protiviti](https://www.tamtam.ai/c/protiviti) (protiviti.com)<br>Global consulting firm offering expertise in finance, technology, operations, data, digital, legal, HR, risk, and internal audit to help clients navigate future challenges | Business Consulting and Services | 🇺🇸 Menlo Park | 13,479 | 2002 |
| 9 | [Capital Group](https://www.tamtam.ai/c/capital-group) (capitalgroup.com)<br>Provides carefully researched investment solutions and services to financial professionals worldwide with a history spanning over 90 years. | Financial Services | 🇺🇸 Los Angeles | 9,761 | 1931 |
| 10 | [Gensler](https://www.tamtam.ai/c/gensler) (gensler.com)<br>Global architecture, design, and planning firm with a network of 6,000+ professionals creating positive change through impactful design across various sectors worldwide | Architecture and Planning | 🇺🇸 San Francisco | 8,363 | 1965 |
| 11 | [URS Corporation, An AECOM Company](https://www.tamtam.ai/c/urs-corporation-an-aecom-company) (urs.com)<br>A global professional and technical services firm offering design, construction, and operations of infrastructure assets worldwide for public and private clients | Civil Engineering | 🇺🇸 San Francisco | 8,221 |  |
| 12 | [Alliant Insurance Services](https://www.tamtam.ai/c/alliant-insurance-services) (alliant.com)<br>Provides innovative insurance brokerage and consulting services, supporting diverse clients with expert teams to help grow businesses and communities. | Insurance Agencies and Brokerages | 🇺🇸 Irvine | 6,616 | 1925 |
| 13 | [AppleOne Employment Services](https://www.tamtam.ai/c/appleone-employment-services) (appleone.com)<br>A full-service employment agency focusing on helping career seekers and finding great employees through personalized solutions for over five decades | Staffing and Recruiting | 🇺🇸 Glendale | 6,277 |  |
| 14 | [Xoriant](https://www.tamtam.ai/c/xoriant) (xoriant.com)<br>Xoriant is a global digital engineering firm that turns imaginative visions into realities, accelerating business outcomes with innovative technology solutions | IT Services and IT Consulting | 🇺🇸 Sunnyvale | 5,220 | 1990 |
| 15 | [Robert Half Finance & Accounting](https://www.tamtam.ai/c/robert-half-finance-and-accounting) (roberthalf.com)<br>Specialized financial recruitment service with experienced recruiters connecting skilled accounting and finance professionals with leading companies worldwide | Staffing and Recruiting | 🇺🇸 Menlo Park | 4,940 |  |
| 16 | [Aricent](https://www.tamtam.ai/c/aricent) (capgemini.com)<br>Legacy engineering firm now merged with Altran specializing in technology services and industrial innovations across various sectors for global business transformation. | Software Development | 🇺🇸 Santa Clara | 4,886 |  |
| 17 | [Houlihan Lokey](https://www.tamtam.ai/c/houlihan-lokey) (hl.com)<br>Global investment bank specializing in mergers and acquisitions, capital solutions, financial restructuring, and valuation advisory services worldwide. | Investment Banking | 🇺🇸 Los Angeles | 4,830 |  |
| 18 | [Creative Artists Agency](https://www.tamtam.ai/c/creative-artists-agency) (caa.com)<br>A global entertainment and sports agency offering services in various fields including talent representation, media finance, and sports properties sales | Entertainment Providers | 🇺🇸 Los Angeles | 4,811 |  |
| 19 | [Tredence Inc.](https://www.tamtam.ai/c/tredence-inc) (tredence.com)<br>Global data science solutions provider, focused on closing the gap between AI insights and tangible business value for clients across various industries. | Business Consulting and Services | 🇺🇸 San Jose | 4,440 | 2013 |
| 20 | [Sama](https://www.tamtam.ai/c/sama) (sama.com)<br>A global leader in data annotation solutions for enterprise AI models, focusing on accuracy, scalability, and ethical practices to advance computer vision AI development | IT Services and IT Consulting | 🇺🇸 San Francisco | 4,350 | 2008 |
| 21 | [Robert Half Technology](https://www.tamtam.ai/c/robert-half-technology) (roberthalf.com)<br>A leading provider of technology professionals for projects ranging from web development to network security, with over 120 worldwide locations | Staffing and Recruiting | 🇺🇸 Suite 200 | 4,196 | 1993 |
| 22 | [eInfochips (An Arrow Company)](https://www.tamtam.ai/c/einfochips-an-arrow-company) (einfochips.com)<br>A global provider of product engineering, semiconductor design, and IoT solutions across various cloud platforms with a focus on innovation and client success | IT Services and IT Consulting | 🇺🇸 San Jose | 4,006 | 1995 |
| 23 | [Express Employment Professionals - Garden Grove](https://www.tamtam.ai/c/express-employment-professionals-garden-grove) (expresspros.com)<br>The company specializes in connecting quality companies with talented individuals, facilitating successful matches for both employers and job seekers | Staffing and Recruiting | 🇺🇸 Garden Grove | 3,920 | 1977 |
| 24 | [THE·TEAM](https://www.tamtam.ai/c/the-team) (the.team)<br>Provides representation, marketing services to talent, brands, properties across sports, music, and entertainment industries. Headquartered in Los Angeles with global presence. | Professional Services | 🇺🇸 Los Angeles | 3,887 |  |
| 25 | [Marcus & Millichap](https://www.tamtam.ai/c/marcus-and-millichap) (marcusmillichap.com)<br>It specializes in real estate investment sales and financing, providing market knowledge and access to inventory for exceptional client results. | Real Estate | 🇺🇸 Calabasas | 3,800 | 1971 |
| 26 | [Bristlecone](https://www.tamtam.ai/c/bristlecone) (bristlecone.com)<br>A leading provider of AI-powered application transformation services for the digital supply chain, offering solutions in digital logistics, manufacturing, planning, procurement, and digitalization | IT Services and IT Consulting | 🇺🇸 San Jose | 3,670 | 1998 |
| 27 | [Legence](https://www.tamtam.ai/c/legence) (wearelegence.com)<br>Integrated provider of energy efficiency and sustainability solutions for diverse industries, specializing in advisory, engineering, contracting, and maintenance services for high-performance facilities | Construction | 🇺🇸 San Jose | 3,648 |  |
| 28 | [Cooley LLP](https://www.tamtam.ai/c/cooley-llp) (cooley.com)<br>A global law firm with 1,300 lawyers specializing in transformative deals, IP, regulatory matters, and litigation across the US, Asia, and Europe | Law Practice | 🇺🇸 Palo Alto | 3,597 | 1920 |
| 29 | [Indium](https://www.tamtam.ai/c/indium) (indium.tech)<br>A fast-growing Digital Engineering company offering modern solutions across Applications, Data, and Gaming with deep expertise in next-gen offerings and partnerships with leading technology companies | IT Services and IT Consulting | 🇺🇸 Cupertino | 3,560 | 1999 |
| 30 | [Andersen](https://www.tamtam.ai/c/andersen) (andersen.com)<br>Global association of independent member firms with 14,000 professionals offering comprehensive solutions in accounting, law, and tax services worldwide With 2,000 personnel in the US | Financial Services | 🇺🇸 San Francisco | 3,560 |  |
| 31 | [Paul Hastings](https://www.tamtam.ai/c/paul-hastings) (paulhastings.com)<br>Premier law firm specializing in finance, mergers, private equity, restructuring, litigation, employment, and real estate for top clients worldwide. | Law Practice | 🇺🇸 Los Angeles | 3,357 | 1951 |
| 32 | [TYLin](https://www.tamtam.ai/c/tylin) (tylin.com)<br>Design infrastructure solutions enhancing mobility, sustainability, resilience, and innovation to connect and elevate communities worldwide with advanced engineering approaches. | Civil Engineering | 🇺🇸 San Francisco | 3,321 |  |
| 33 | [Hitachi Digital Services](https://www.tamtam.ai/c/hitachi-digital-services) (hitachids.com)<br>An independent services business specializing in cloud, data, IoT, and managed services, utilizing Generative AI for integrated digital transformation solutions for enterprises | IT Services and IT Consulting | 🇺🇸 Santa Clara | 3,297 |  |
| 34 | [Armanino](https://www.tamtam.ai/c/armanino) (armanino.com)<br>A leading CPA & consulting firm offering top-tier services with a strong community commitment, industry expertise, and personal client attention | Accounting | 🇺🇸 San Ramon | 3,297 | 1969 |
| 35 | [Gordon Rees Scully Mansukhani, LLP](https://www.tamtam.ai/c/gordon-rees-scully-mansukhani-llp) (grsm.com)<br>A nationwide law firm providing comprehensive litigation and business transaction services to public and private companies, with 1,200 lawyers across all states | Law Practice | 🇺🇸 San Francisco | 3,257 | 1974 |
| 36 | [Lewis Brisbois](https://www.tamtam.ai/c/lewis-brisbois) (lewisbrisbois.com)<br>A national law firm established in 1979, with over 1,600 attorneys and 54 offices in 30 states, providing full-service legal assistance | Law Practice | 🇺🇸 Los Angeles | 3,225 | 1979 |
| 37 | [Orrick, Herrington & Sutcliffe LLP](https://www.tamtam.ai/c/orrick-herrington-and-sutcliffe-llp) (orrick.com)<br>Global law firm specializing in technology, energy, infrastructure, and finance sectors, providing pragmatic advice on transactions, litigation, and compliance worldwide. | Law Practice | 🇺🇸 San Francisco | 3,193 | 1863 |
| 38 | [BairesDev](https://www.tamtam.ai/c/bairesdev) (bairesdev.com)<br>Expert partner in building high-quality software solutions with top tech talent Delivering scalable technology solutions for startups to Fortune Global 500 brands Unlocking business possibilities | IT Services and IT Consulting | 🇺🇸 San Francisco | 3,174 | 2009 |
| 39 | [Milestone Technologies, Inc.](https://www.tamtam.ai/c/milestone-technologies-inc) (milestone.tech)<br>A global IT services and digital solutions company in Silicon Valley, specializing in application services, digital product engineering, and workplace services | IT Services and IT Consulting | 🇺🇸 Fremont | 3,008 | 1997 |
| 40 | [Morrison Foerster](https://www.tamtam.ai/c/morrison-foerster) (mofo.com)<br>Providing tailored legal strategies and trusted partnerships to solve complex challenges for financial, technology, life sciences, and Fortune 100 clients. | Law Practice | 🇺🇸 San Francisco | 2,990 | 1883 |
| 41 | [Littler](https://www.tamtam.ai/c/littler) (littler.com)<br>Largest global employment and labor law practice representing management, providing comprehensive legal solutions across multiple continents and countries worldwide. | Law Practice | 🇺🇸 San Francisco | 2,984 | 1942 |
| 42 | [TPG](https://www.tamtam.ai/c/tpg-san-francisco) (tpg.com)<br>Global alternative asset management firm focused on private equity, impact, credit, real estate, and market solutions through collaborative and innovative investment strategies. | Financial Services | 🇺🇸 San Francisco | 2,975 | 1992 |
| 43 | [Pearce Services](https://www.tamtam.ai/c/pearce-services) (pearce-services.com)<br>Provider of repair, maintenance, and engineering services for critical infrastructure in renewable energy, power generation, and telecom industries, with tech-enabled solutions nationwide | Telecommunications | 🇺🇸 Paso Robles | 2,961 |  |
| 44 | [Taller](https://www.tamtam.ai/c/taller-san-francisco) (taller.us)<br>The company uses AI to provide expertly-matched tech teams from Latin America, helping businesses accelerate growth, reduce hiring time, and improve retention | IT Services and IT Consulting | 🇺🇸 San Francisco | 2,669 | 2008 |
| 45 | [Kleinfelder](https://www.tamtam.ai/c/kleinfelder) (kleinfelder.com)<br>Engineering, science, and construction firm offering solutions for transportation, water, energy, and private infrastructure projects with a dedicated, cross-disciplinary team | Civil Engineering | 🇺🇸 San Diego | 2,656 |  |
| 46 | [Cetera Financial Group](https://www.tamtam.ai/c/cetera-financial-group) (cetera.com)<br>Network of independent retail financial firms providing technology, guidance, research, and collaborative platforms for financial professionals and investors. | Financial Services | 🇺🇸 San Diego | 2,653 | 1981 |
| 47 | [Brown and Caldwell](https://www.tamtam.ai/c/brown-and-caldwell) (brownandcaldwell.com)<br>Privately-held environmental firm specializing in US water and environmental sectors Offering engineering, scientific, consulting, and construction services globally Passionate about innovation and service excellence | Environmental Services | 🇺🇸 Walnut Creek | 2,556 | 1947 |
| 48 | [HAND Enterprise Solutions LTD.](https://www.tamtam.ai/c/hand-enterprise-solutions-ltd) (hand-us.com)<br>Global software service provider with 20 years of experience specializing in ORACLE and SAP implementations across multiple industries worldwide | IT Services and IT Consulting | 🇺🇸 Milpitas | 2,555 | 1996 |
| 49 | [DCS](https://www.tamtam.ai/c/dcs) (webdcs.com)<br>Company provides Education & Training, Research & Engineering, and Information Technology Solutions to the Federal Government as their preferred contractor | IT Services and IT Consulting | 🇺🇸 Newbury Park | 2,497 | 1994 |
| 50 | [HTEC](https://www.tamtam.ai/c/htec-palo-alto) (htec.com)<br>Global digital consulting firm providing innovative product design and technology engineering services to high-tech companies, startups, and enterprises worldwide | IT Services and IT Consulting | 🇺🇸 Palo Alto | 2,449 |  |
| 51 | [United Talent Agency](https://www.tamtam.ai/c/united-talent-agency) (unitedtalent.com)<br>A global entertainment company representing iconic artists and creators, offering talent representation, content production, strategic advisory, and marketing services to top brands | Entertainment Providers | 🇺🇸 Beverly Hills | 2,405 | 1991 |
| 52 | [Sheppard](https://www.tamtam.ai/c/sheppard) (sheppard.com)<br>Provides comprehensive legal services including corporate, technology, litigation, financial transactions, intellectual property, labor, real estate, and government contracts. | Law Practice | 🇺🇸 Los Angeles | 2,397 | 1927 |
| 53 | [Wilson Sonsini Goodrich & Rosati](https://www.tamtam.ai/c/wilson-sonsini-goodrich-and-rosati) (wsgr.com)<br>Leading legal advisor to technology, life sciences, and growth enterprises worldwide Specializing in corporate governance, finance, M&A, IP, and more Active alumni network available | Law Practice | 🇺🇸 Palo Alto | 2,340 | 1961 |
| 54 | [Power Digital Marketing](https://www.tamtam.ai/c/power-digital-marketing) (powerdigitalmarketing.com)<br>Growth marketing firm utilizing proprietary technology to analyze digital ecosystems and develop custom data-driven playbooks for revenue growth and brand recognition worldwide. | Advertising Services | 🇺🇸 San Diego | 2,318 | 2012 |
| 55 | [Sullivan & Cromwell LLP](https://www.tamtam.ai/c/sullivan-and-cromwell-llp) (sullcrom.com)<br>A global law firm with 140 years of experience, offering high-quality legal advice and representation through a network of 13 offices worldwide | Law Practice | 🇺🇸 Manhattan | 2,311 |  |
| 56 | [Salas O'Brien](https://www.tamtam.ai/c/salas-o-brien) (salasobrien.com)<br>Employee-owned engineering firm focused on advancing the human experience through the built environment Top-ranked, with a strong emphasis on impact and sustainability | Engineering Services | 🇺🇸 Irvine | 2,295 | 1975 |
| 57 | [PrideStaff](https://www.tamtam.ai/c/pridestaff) (pridestaff.com)<br>This company focuses on providing exceptional client service and quality candidates, personalized solutions, building loyalty, and celebrating success in the staffing industry | Staffing and Recruiting | 🇺🇸 Fresno | 2,291 | 1978 |
| 58 | [Korn Ferry Futurestep](https://www.tamtam.ai/c/korn-ferry-futurestep) (kornferry.com)<br>Futurestep, a division of Korn Ferry, provides innovative talent solutions through data-driven insights, strategic collaboration, and advanced technology | Staffing and Recruiting | 🇺🇸 Los Angeles | 2,251 | 1998 |
| 59 | [LNT Infotech](https://www.tamtam.ai/c/lnt-infotech) (lntinfotech.com)<br>A global IT solutions & services company, part of Larsen & Toubro, helping clients succeed in digital transformation through technology consulting and digital solutions | IT Services and IT Consulting | 🇺🇸 Santa Clara | 2,230 | 1947 |
| 60 | [GSPANN Technologies, Inc](https://www.tamtam.ai/c/gspann-technologies-inc) (gspann.com)<br>Consulting services specializing in ECM, business intelligence, big data, mobility, and DevOps for Fortune 1000 clients. | Software Development | 🇺🇸 Milpitas | 2,200 | 2004 |
| 61 | [Quinn Emanuel](https://www.tamtam.ai/c/quinn-emanuel) (quinnemanuel.com)<br>Global business litigation firm specializing in arbitration, achieving high success rates and securing substantial verdicts and settlements for clients. | Law Practice | 🇺🇸 Los Angeles | 2,135 | 1986 |
| 62 | [Jade Global](https://www.tamtam.ai/c/jade-global) (jadeglobal.com)<br>consulting, integration, and managed services partner helping enterprises modernize, innovate, and scale with cloud transformation, ERP, CRM, data analytics, and AI automation. | IT Services and IT Consulting | 🇺🇸 San Jose | 2,125 | 2003 |
| 63 | [Robert Half Management Resources](https://www.tamtam.ai/c/robert-half-management-resources-menlo-park) (roberthalf.com)<br>A leading provider of senior financial and business systems professionals for interim roles worldwide, specializing in finance, IT, audit, and more | Staffing and Recruiting | 🇺🇸 Menlo Park | 2,125 |  |
| 64 | [Nisum](https://www.tamtam.ai/c/nisum) (nisum.com)<br>Global consulting partner specializing in digital commerce and evolution, building AI-powered platforms and tailor-made solutions for growth, optimized operations, and long-term value. | IT Services and IT Consulting | 🇺🇸 Brea | 2,119 | 2000 |
| 65 | [MAP](https://www.tamtam.ai/c/map-sherman-oaks) (mapconsulting.com)<br>A performance improvement consulting firm offering a proven Management System™ to drive profitability, productivity, and breakthrough results for businesses | Business Consulting and Services | 🇺🇸 Sherman Oaks | 2,119 | 1960 |
| 66 | [frog](https://www.tamtam.ai/c/frog) (frog.co)<br>Innovative global consultancy part of Capgemini Invent, crafting transformative human experiences through creativity, strategy, design, and data for business growth | Design Services | 🇺🇸 San Francisco | 2,103 | 1969 |
| 67 | [Lollypop Design Studio](https://www.tamtam.ai/c/lollypop-design-studio) (lollypop.design)<br>Harnessing design and technology to create transformative digital experiences, specializing in research-driven design and development across various industries | Design Services | 🇺🇸 San Jose | 2,088 |  |
| 68 | [Scoot Education](https://www.tamtam.ai/c/scoot-education) (scoot.education)<br>A company dedicated to placing exceptional teachers in educational settings through personalized service, tech-based solutions, and an innovative earn-and-learn academy | Staffing and Recruiting | 🇺🇸 Los Angeles | 2,051 | 2017 |
| 69 | [Creative Circle](https://www.tamtam.ai/c/creative-circle) (creativecircle.com)<br>Creative Circle offers marketing and creative services to help companies tackle business challenges through talent acquisition, studio and agency support, flex benches, and consulting | Staffing and Recruiting | 🇺🇸 Los Angeles | 2,013 | 2001 |
| 70 | [Outsource](https://www.tamtam.ai/c/outsource) (outsource.net)<br>National staffing firm providing qualified technicians for temporary and permanent placement in low voltage and electrical roles, with 22 locations nationwide | Staffing and Recruiting | 🇺🇸 El Segundo | 1,962 | 1998 |
| 71 | [E-Solutions](https://www.tamtam.ai/c/e-solutions) (e-solutionsinc.com)<br>A talent-driven talent acquisition company offering workforce, cloud, salesforce, global payrolling, MSP/VMO, EOR & AOR services with global presence and industry expertise | IT Services and IT Consulting | 🇺🇸 San Jose | 1,961 | 2003 |
| 72 | [WME \| William Morris Endeavor](https://www.tamtam.ai/c/wme-william-morris-endeavor) (wmeagency.com)<br>A leading entertainment agency representing top artists, creators, and talent across various industries, part of a global sports and entertainment company | Entertainment Providers | 🇺🇸 Beverly Hills | 1,920 | 1898 |
| 73 | [KCC](https://www.tamtam.ai/c/kcc) (veritaglobal.com)<br>A leading claims and noticing agent offering administrative support services and consulting for companies undergoing corporate restructurings with innovative technologies and experienced staff | Legal Services | 🇺🇸 El Segundo | 1,905 | 2001 |
| 74 | [Innominds](https://www.tamtam.ai/c/innominds) (innominds.com)<br>AI-first platform-led digital transformation and full cycle product engineering services specializing in devices, embedded engineering, software apps, analytics, cloud, and security. | IT Services and IT Consulting | 🇺🇸 San Jose | 1,888 | 1998 |
| 75 | [BPM LLP](https://www.tamtam.ai/c/bpm-llp) (bpm.com)<br>Top 35 US public accounting firm in various industries, recognized for fast growth Offers diverse, progressive solutions as certified B Corp | Business Consulting and Services | 🇺🇸 San Francisco | 1,864 | 1986 |
| 76 | [Q](https://www.tamtam.ai/c/q) (qconnects.com)<br>An IT & Digital recruitment firm specializing in delivering qualified and diverse talent for technology, product, and digital roles nationwide | Staffing and Recruiting | 🇺🇸 Los Angeles | 1,806 |  |
| 77 | [Carollo Engineers](https://www.tamtam.ai/c/carollo-engineers) (carollo.com)<br>Specializing solely in water related engineering, we provide innovative solutions, unparalleled client service, and a collaborative working environment since 1933 | Environmental Services | 🇺🇸 Walnut Creek | 1,803 | 1933 |
| 78 | [ADEC Innovations](https://www.tamtam.ai/c/adec-innovations) (adec-innovations.com)<br>ADEC Innovations offers integrated industry expertise, data management, and software services to meet ESG needs, improve sustainability performance, and drive operational efficiencies globally | Business Consulting and Services | 🇺🇸 Irvine | 1,801 |  |
| 79 | [OfficeTeam](https://www.tamtam.ai/c/officeteam) (roberthalf.com)<br>Leading staffing service specializing in placing skilled office and administrative support professionals on temporary and temporary-to-full-time basis worldwide Offering superior training and resources to candidates | Staffing and Recruiting | 🇺🇸 San Ramon | 1,783 |  |
| 80 | [GHJ](https://www.tamtam.ai/c/ghj) (ghjadvisors.com)<br>National advisory and accounting firm serving clients globally in nonprofit, food and beverage, entertainment, and health industries, leveraging a global network for comprehensive services (Note: This summary is based on the provided content without mentioning the company name) | Accounting | 🇺🇸 Los Angeles | 1,768 | 1953 |
| 81 | [ChildCare Careers](https://www.tamtam.ai/c/childcare-careers) (childcarecareers.com)<br>Staffing firm specializing in providing fully qualified teachers and directors to child care centers and programs, offering on-demand substitutes for short or long-term assignments | Staffing and Recruiting | 🇺🇸 Brisbane | 1,763 | 1996 |
| 82 | [Host Healthcare, Inc.](https://www.tamtam.ai/c/host-healthcare-inc) (hosthealthcare.com)<br>Travel healthcare staffing agency specializing in nursing, allied, and therapy jobs Award-winning team with top ratings and recognized as a top employer | Hospitals and Health Care | 🇺🇸 San Diego | 1,701 | 2012 |
| 83 | [Wizeline](https://www.tamtam.ai/c/wizeline) (wizeline.ai)<br>A global technology services provider that builds digital products & platforms, modernizes core technologies, enhances data-driven capabilities, & improves user experience | IT Services and IT Consulting | 🇺🇸 San Francisco | 1,800 | 2014 |
| 84 | [Sequoia](https://www.tamtam.ai/c/sequoia) (sequoia.com)<br>Sequoia specializes in total people investment, helping companies optimize outcomes through comprehensive rewards, including compensation, benefits, wellbeing, HR, payroll, and business protection | Business Consulting and Services | 🇺🇸 San Mateo | 1,607 | 2001 |
| 85 | [B. Riley Financial](https://www.tamtam.ai/c/b-riley-financial) (brcgh.com)<br>Provides diverse collaborative solutions in capital raising, business advisory, investment banking, wealth management, financial consulting, corporate restructuring, risk/compliance, and more | Financial Services | 🇺🇸 Los Angeles | 1,596 | 1997 |
| 86 | [Edge](https://www.tamtam.ai/c/edge-mountain-view) (onedge.co)<br>This company offers a global HR solution connecting talent worldwide with businesses in North America, aiming to eliminate geographic barriers in hiring | Human Resources Services | 🇺🇸 Mountain View | 1,567 | 2022 |
| 87 | [Jobot](https://www.tamtam.ai/c/jobot) (jobot.com)<br>Jobot disrupts recruiting by combining AI with skilled recruiters for job placements, focusing on positive culture, respect, and lasting careers | Staffing and Recruiting | 🇺🇸 Newport Beach | 1,539 | 2018 |
| 88 | [Programming.com](https://www.tamtam.ai/c/programming-com) (programming.com)<br>The company specializes in providing efficient and cost-effective software solutions in various cutting-edge technologies and services for digital transformation | IT Services and IT Consulting | 🇺🇸 Los Angeles | 1,494 | 2001 |
| 89 | [Mandiant (part of Google Cloud)](https://www.tamtam.ai/c/mandiant-part-of-google-cloud) (cloud.google.com)<br>Dedicated to making organizations secure against cyber threats and confident in their readiness through trusted cybersecurity solutions, now from Google Cloud. | Computer and Network Security | 🇺🇸 Mountain View | 1,454 | 2004 |
| 90 | [IDEO](https://www.tamtam.ai/c/ideo) (ideo.com)<br>This company helps individuals and organizations design innovative products and services to create a more sustainable and equitable future | Design Services | 🇺🇸 San Francisco | 1,443 |  |
| 91 | [Trace3](https://www.tamtam.ai/c/trace3) (trace3.com)<br>Consulting on, integrating, and operating data, security, and cloud solutions to drive business transformation and create measurable value for clients | IT Services and IT Consulting | 🇺🇸 Irvine | 1,440 | 2002 |
| 92 | [Partner Engineering & Science, Inc.](https://www.tamtam.ai/c/partner-engineering-and-science-inc) (partneresi.com)<br>National firm providing engineering, environmental, and energy consulting services, from due diligence to design, construction, maintenance, and compliance in various industries | Environmental Services | 🇺🇸 Torrance | 1,438 | 2007 |
| 93 | [OSI Digital](https://www.tamtam.ai/c/osi-digital) (osidigital.com)<br>A global provider of business and technology solutions, specializing in digital transformation, data optimization, and system integration for a wide range of industries | IT Services and IT Consulting | 🇺🇸 Calabasas | 1,436 | 1993 |
| 94 | [CCG](https://www.tamtam.ai/c/ccg-pasadena) (ccg.com)<br>A national tax credit consulting firm in Pasadena, CA, specializing in helping companies maximize hiring-based and location-based tax credits | Accounting | 🇺🇸 Pasadena | 1,417 | 2002 |
| 95 | [Grazitti Interactive](https://www.tamtam.ai/c/grazitti-interactive) (grazitti.com)<br>Providing marketing automation, sales optimization, and cloud innovation services with global partnerships and strong compliance certifications for data security. | IT Services and IT Consulting | 🇺🇸 Mountain View | 1,416 | 2008 |
| 96 | [ENG](https://www.tamtam.ai/c/eng) (engbim.com)<br>A leading BIM company specializing in MEP modeling, VDC management, laser scanning, and BIM services across multiple industries in the US and Latin America | Construction | 🇺🇸 Newport Beach | 1,410 | 1989 |
| 97 | [Self-employed](https://www.tamtam.ai/c/self-employed-san-francisco) (quesben.com)<br>Freelance communications & strategy consultant specializing in promoting alternative living solutions like sustainability, minimalism, and modern nomadism for purpose-driven leaders and entrepreneurs | Advertising Services | 🇺🇸 San Francisco | 1,392 | 2018 |
| 98 | [Cornerstone Research](https://www.tamtam.ai/c/cornerstone-research) (cornerstone.com)<br>Provides economic and financial analysis for litigation, utilizing academic experts and innovative research methods to solve complex legal and business problems. | Business Consulting and Services | 🇺🇸 San Francisco | 1,359 | 1989 |
| 99 | [HOSPITALITY recruiter recruiters EXECUTIVE search hotel chef restaurant manager +1-310-691-2586](https://www.tamtam.ai/c/hospitality-recruiter-recruiters-executive-search-hotel-chef-restaurant-manager) (hospitalityexecutive.com)<br>An international hospitality recruitment firm specializing in luxury hotel, restaurant, and chef placements across various countries and regions worldwide | Hospitality | 🇺🇸 Beverly Hills | 1,339 | 1987 |
| 100 | [IA Interior Architects](https://www.tamtam.ai/c/ia-interior-architects) (interiorarchitects.com)<br>An innovative global architecture firm specializing in interior design, providing strategic planning, architecture, and design services for corporations and institutions worldwide | Design Services | 🇺🇸 San Francisco | 1,321 | 1984 |

## How this list is built

Every company on this list has a Tamtam company profile. The industry is the one the company gives on LinkedIn; categories such as SaaS or fintech are classified by Tamtam's AI from the company's website and LinkedIn page; and the headquarters city must match the company's own address. Companies are ranked by the number of employees on LinkedIn, and the list is refreshed every night. Classifications can be wrong, so treat the list as a starting point rather than an official ranking. Last updated Nov 11, 2026.

## More company lists in California

- [The largest companies in California](https://www.tamtam.ai/l/largest-companies-california) (15,265)
- [Multinational companies in California](https://www.tamtam.ai/l/multinational-companies-california) (2,592)
- [SaaS companies in California](https://www.tamtam.ai/l/saas-companies-california) (1,855)
- [Software Development companies in California](https://www.tamtam.ai/l/software-development-companies-california) (1,650)
- [AI companies in California](https://www.tamtam.ai/l/ai-companies-california) (1,297)
- [Companies with in-house R&D in California](https://www.tamtam.ai/l/r-and-d-companies-california) (1,276)
- [Manufacturers in California](https://www.tamtam.ai/l/manufacturers-california) (1,066)
- [Hardware manufacturers in California](https://www.tamtam.ai/l/hardware-companies-california) (985)
- [IT Services and IT Consulting companies in California](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-california) (968)
- [Education providers in California](https://www.tamtam.ai/l/education-companies-california-united-states) (950)
- [Subscription businesses in California](https://www.tamtam.ai/l/subscription-businesses-california) (940)
- [Venture capital and private equity firms in California](https://www.tamtam.ai/l/vc-and-private-equity-firms-california) (917)
- [Companies with a mobile app in California](https://www.tamtam.ai/l/companies-with-mobile-app-california) (827)
- [Retail chains in California](https://www.tamtam.ai/l/retail-chains-california) (803)
- [IT services companies in California](https://www.tamtam.ai/l/it-services-companies-california) (796)
- [Venture Capital and Private Equity Principals companies in California](https://www.tamtam.ai/l/venture-capital-and-private-equity-principals-companies-california) (731)
- [Financial services firms in California](https://www.tamtam.ai/l/financial-services-firms-california) (711)
- [Financial Services companies in California](https://www.tamtam.ai/l/financial-services-companies-california) (642)
- [Healthcare providers in California](https://www.tamtam.ai/l/healthcare-providers-california) (569)
- [AI-native companies in California](https://www.tamtam.ai/l/ai-native-companies-california) (561)
- [Hospitals and Health Care companies in California](https://www.tamtam.ai/l/hospitals-and-health-care-companies-california) (555)
- [Consulting firms in California](https://www.tamtam.ai/l/consulting-firms-california) (551)
- [Public sector organisations in California](https://www.tamtam.ai/l/public-sector-organisations-california) (535)
- [Technology, Information and Internet companies in California](https://www.tamtam.ai/l/technology-information-and-internet-companies-california) (514)

## The same list elsewhere in United States

- [Professional services firms in the United States](https://www.tamtam.ai/l/professional-services-firms-united-states) (7,078)
- [Professional services firms in New York State](https://www.tamtam.ai/l/professional-services-firms-new-york-state) (955)
- [Professional services firms in Texas](https://www.tamtam.ai/l/professional-services-firms-texas) (629)
- [Professional services firms in Florida](https://www.tamtam.ai/l/professional-services-firms-florida) (375)
- [Professional services firms in Virginia](https://www.tamtam.ai/l/professional-services-firms-virginia) (344)
- [Professional services firms in Illinois](https://www.tamtam.ai/l/professional-services-firms-illinois) (339)
- [Professional services firms in Massachusetts](https://www.tamtam.ai/l/professional-services-firms-massachusetts) (249)
- [Professional services firms in New Jersey](https://www.tamtam.ai/l/professional-services-firms-new-jersey) (249)
- [Professional services firms in Georgia](https://www.tamtam.ai/l/professional-services-firms-georgia) (246)
- [Professional services firms in Pennsylvania](https://www.tamtam.ai/l/professional-services-firms-pennsylvania) (245)
- [Professional services firms in Ohio](https://www.tamtam.ai/l/professional-services-firms-ohio) (195)
- [Professional services firms in Maryland](https://www.tamtam.ai/l/professional-services-firms-maryland) (176)
- [Professional services firms in Michigan](https://www.tamtam.ai/l/professional-services-firms-michigan) (172)
- [Professional services firms in Washington State](https://www.tamtam.ai/l/professional-services-firms-washington-state) (163)
- [Professional services firms in North Carolina](https://www.tamtam.ai/l/professional-services-firms-north-carolina) (142)
- [Professional services firms in Alabama](https://www.tamtam.ai/l/professional-services-firms-alabama) (135)
- [Professional services firms in Minnesota](https://www.tamtam.ai/l/professional-services-firms-minnesota) (125)
- [Professional services firms in New York](https://www.tamtam.ai/l/professional-services-firms-new-york) (735)
- [Professional services firms in Chicago](https://www.tamtam.ai/l/professional-services-firms-chicago) (196)
- [Professional services firms in Houston](https://www.tamtam.ai/l/professional-services-firms-houston) (156)
- [Professional services firms in Atlanta](https://www.tamtam.ai/l/professional-services-firms-atlanta) (143)
- [Professional services firms in San Francisco](https://www.tamtam.ai/l/professional-services-firms-san-francisco) (130)
- [Professional services firms in Washington](https://www.tamtam.ai/l/professional-services-firms-washington) (109)
- [Professional services firms in Los Angeles](https://www.tamtam.ai/l/professional-services-firms-los-angeles) (108)

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Source: https://www.tamtam.ai/l/professional-services-firms-california