# Professional services firms headquartered in Irvine

Tamtam tracks 61 professional services firms headquartered in Irvine. This list ranks the 30 largest by number of employees on LinkedIn, led by Allied Universal, Alliant Insurance Services and Salas O'Brien. Their median headcount is 582. Half of them were founded in 1999 or later.

These professional services firms in Irvine largely operate in IT consulting, staffing, and environmental services. The companies listed are primarily mid-sized to large organizations. Notable firms include Allied Universal, a security and facility services provider with over 100,000 employees, and Alliant Insurance Services, an insurance brokerage founded in 1925. Salas O'Brien is an employee-owned engineering firm, while ADEC Innovations specializes in ESG data management.

The data shows a strong presence of companies founded in the 1970s and 1980s, indicating a mature business environment. Many firms, such as Trace3 and Neudesic, an IBM Company, focus on IT services, cloud solutions, and digital modernization, reflecting a significant technology services cluster within Irvine.

🇺🇸 Irvine · 30 companies · Updated Nov 12, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [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 |  |
| 2 | [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 |
| 3 | [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 |
| 4 | [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 |  |
| 5 | [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 |
| 6 | [JAMS](https://www.tamtam.ai/c/jams) (jamsadr.com)<br>JAMS provides efficient, impartial dispute resolution services globally, with industry-specific experience, top-notch facilities, and highly trained panelists for optimal outcomes | Alternative Dispute Resolution | 🇺🇸 Irvine | 1,097 | 1979 |
| 7 | [Caylent](https://www.tamtam.ai/c/caylent) (caylent.com)<br>Cloud native services provider helping organizations optimize people and technology with AWS, enabling innovation and ambitious ideas to thrive | IT Services and IT Consulting | 🇺🇸 Irvine | 899 | 2015 |
| 8 | [Kimco Staffing Services, Inc.](https://www.tamtam.ai/c/kimco-staffing-services-inc) (kimco.com)<br>A trusted staffing agency offering office, accounting, technical, industrial, and call center placements with over 30 years of award-winning service | Staffing and Recruiting | 🇺🇸 Irvine | 857 | 1986 |
| 9 | [Neudesic, an IBM Company](https://www.tamtam.ai/c/neudesic-an-ibm-company) (neudesic.com)<br>Trusted technology partner specializing in digital modernization, custom application development, managed services, and business software products for impactful business results | IT Services and IT Consulting | 🇺🇸 Irvine | 800 | 2002 |
| 10 | [LPA, Inc.](https://www.tamtam.ai/c/lpa-inc) (lpadesignstudios.com)<br>LPA is a design firm focused on creating timeless, sustainable projects that benefit the environment, enrich human experiences, and inspire innovation | Architecture and Planning | 🇺🇸 Irvine | 731 | 1965 |
| 11 | [FCS](https://www.tamtam.ai/c/fcs) (firstcarbonsolutions.com)<br>Leading provider of environmental, sustainability, and compliance solutions with expertise in CEQA/NEPA, compliance, permitting, natural resources management, and more Join our team! | Environmental Services | 🇺🇸 Irvine | 613 | 1982 |
| 12 | [CyberCoders](https://www.tamtam.ai/c/cybercoders) (cybercoders.com)<br>A leading recruiting firm with skilled recruiters filling thousands of positions across various industries using proprietary technology for successful placements | Staffing and Recruiting | 🇺🇸 Irvine | 608 | 1999 |
| 13 | [Knobbe Martens](https://www.tamtam.ai/c/knobbe-martens) (knobbe.com)<br>A highly respected intellectual property law firm with a team of 300 lawyers and scientists, serving a diverse international client base | Law Practice | 🇺🇸 Irvine | 607 | 1962 |
| 14 | [Hitachi Solutions America](https://www.tamtam.ai/c/hitachi-solutions-america) (global.hitachi-solutions.com)<br>Global IT consulting firm specializing in Microsoft platform solutions, delivering sustainable business modernization and empowering customer growth worldwide. | IT Services and IT Consulting | 🇺🇸 Irvine | 589 | 1971 |
| 15 | [LSA](https://www.tamtam.ai/c/lsa) (lsa.net)<br>A diversified environmental, transportation, and community planning firm offering expert services in various fields, operating across nine California offices | Environmental Services | 🇺🇸 Irvine | 582 | 1976 |
| 16 | [Altezzasys INC](https://www.tamtam.ai/c/altezzasys-inc) (altezzasys.com)<br>A global technology services provider offering staffing, outsourcing, consulting, and digital solutions to align technology innovation with business strategy worldwide | IT Services and IT Consulting | 🇺🇸 Irvine | 571 | 2014 |
| 17 | [Denken Solutions, Inc.](https://www.tamtam.ai/c/denken-solutions-inc) (denkensolutions.com)<br>This company provides Staffing Services, SAP Solutions, and Digital Transformation Services in the IT, Engineering, and Healthcare sectors | Staffing and Recruiting | 🇺🇸 Irvine | 560 | 2010 |
| 18 | [KTGY](https://www.tamtam.ai/c/ktgy) (ktgy.com)<br>Award-winning design firm specializing in architecture, branding, interiors, and planning, dedicated to innovation, creativity, and making a positive impact on communities | Architecture and Planning | 🇺🇸 Irvine | 528 |  |
| 19 | [The Management Trust](https://www.tamtam.ai/c/the-management-trust) (managementtrust.com)<br>A national property management firm specializing in serving condo and homeowner associations, with 100% employee ownership and a strong focus on customer service | Real Estate | 🇺🇸 Irvine | 494 | 2005 |
| 20 | [Renovo Solutions](https://www.tamtam.ai/c/renovo-solutions) (renovo1.com)<br>Provider of Healthcare Technology Management programs offering biomedical imaging services, cybersecurity solutions, equipment maintenance cost reduction, technology management consultation, and unbiased capital equipment planning | Hospitals and Health Care | 🇺🇸 Irvine | 491 | 2009 |
| 21 | [Trio](https://www.tamtam.ai/c/trio) (trioadvisory.com)<br>Global energy and sustainability advisory helping large clients transition to a net-zero future through strategy, implementation, and advanced technological solutions | Business Consulting and Services | 🇺🇸 Irvine | 475 | 2013 |
| 22 | [Resources Global Professionals](https://www.tamtam.ai/c/resources-global-professionals) (rgp.com)<br>Specializing in enterprise risk management consulting to help businesses identify, assess, and mitigate risks for improved decision-making and operational success | Business Consulting and Services | 🇺🇸 Irvine | 459 | 1996 |
| 23 | [Stretto](https://www.tamtam.ai/c/stretto) (stretto.com)<br>Provider of comprehensive case-management, depository solutions, loan-modification services, and technology tools for legal professionals and fiduciaries in the bankruptcy industry | Business Consulting and Services | 🇺🇸 Irvine | 408 | 1987 |
| 24 | [Authority Partners](https://www.tamtam.ai/c/authority-partners) (authoritypartners.com)<br>Global technology strategy consulting and custom software development company delivering digital transformation solutions to increase engagement, sales, productivity, and create value for clients | IT Services and IT Consulting | 🇺🇸 Irvine | 390 | 1998 |
| 25 | [Medical Billing](https://www.tamtam.ai/c/medical-billing) (aplusbillers.com)<br>Trusted medical billing company offering personalized revenue cycle management solutions to healthcare providers, prioritizing accuracy, efficiency, and compliance | Business Consulting and Services | 🇺🇸 Irvine | 361 | 2006 |
| 26 | [Rutan & Tucker, LLP](https://www.tamtam.ai/c/rutan-and-tucker-llp) (rutan.com)<br>The company is a leading full-service business law firm in Orange County, representing a diverse range of clients nationwide | Law Practice | 🇺🇸 Irvine | 348 |  |
| 27 | [Tax Relief Advocates](https://www.tamtam.ai/c/tax-relief-advocates) (tra.com)<br>Specializing in tax debt relief services, we assist individuals facing wage garnishments, bank levies, audits, and other tax-related issues for financial relief | Accounting | 🇺🇸 Irvine | 321 | 2017 |
| 28 | [SMA: The Program Lifecycle Company](https://www.tamtam.ai/c/sma-the-program-lifecycle-company) (smawins.com)<br>SMA helps companies enhance competitiveness through consulting, program management, and technical support, guided by values of professionalism, impact, and courage | Professional Services | 🇺🇸 Irvine | 311 | 1982 |
| 29 | [Kahana Feld](https://www.tamtam.ai/c/kahana-feld) (kahanafeld.com)<br>An award-winning law firm with top litigators, proven success, client satisfaction, diverse culture, collaboration, creativity, superior results, and service | Law Practice | 🇺🇸 Irvine | 278 | 2017 |
| 30 | [SETA International](https://www.tamtam.ai/c/seta-international) (seta-international.com)<br>Global leader in custom software development, specializing in end-to-end technology services and solutions for over 500 clients across a variety of industries worldwide | IT Services and IT Consulting | 🇺🇸 Irvine | 278 | 2008 |

## 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 12, 2026.

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