# Professional services firms headquartered in Washington State

Tamtam tracks 163 professional services firms headquartered in Washington State. This list ranks the 50 largest by number of employees on LinkedIn, led by Avanade, Appen and TrueBlue Inc.. Their median headcount is 1,138. Half of them were founded in 1995 or later. The most common headquarters are Seattle (23), Bellevue (9) and Redmond (4).

This list features large professional services firms in Washington State. It includes several IT services and consulting companies, such as Avanade, which offers digital and cloud advisory services, and Appen, focused on high-quality datasets for AI model training. Other notable firms are Slalom, a consulting firm delivering strategy and technology solutions, and Perkins Coie, a law practice.

The companies on this list are predominantly large, well-established firms, with many founded in the late 20th or early 21st century. A significant cluster of headquarters is located in Seattle, indicating its role as a hub for professional services in the region.

🇺🇸 Washington State · 50 companies · Updated Nov 11, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [Avanade](https://www.tamtam.ai/c/avanade) (avanade.com)<br>Innovative provider of digital, cloud, and advisory services within the Microsoft ecosystem, focused on making a human impact, solving challenges, and promoting sustainability and diversity | IT Services and IT Consulting | 🇺🇸 Seattle | 50,000 | 2000 |
| 2 | [Appen](https://www.tamtam.ai/c/appen) (appen.com)<br>High-quality datasets and human-in-the-loop services for training, fine-tuning, and evaluating generative AI models through a global crowd of over one million contributors. | IT Services and IT Consulting | 🇺🇸 Kirkland | 20,860 | 1996 |
| 3 | [TrueBlue Inc.](https://www.tamtam.ai/c/trueblue-inc) (trueblue.com)<br>Staffing, recruiting, and workforce management services for diverse industries, providing reliable and efficient workforce solutions daily. | Staffing and Recruiting | 🇺🇸 Tacoma | 12,447 | 1989 |
| 4 | [Slalom](https://www.tamtam.ai/c/slalom) (slalom.com)<br>Consulting firm delivering strategy, technology, and data-driven solutions to improve operations, customer experiences, and sustainable growth globally. | Business Consulting and Services | 🇺🇸 Seattle | 10,268 | 2001 |
| 5 | [Aegis](https://www.tamtam.ai/c/aegis-seattle) (aegisgrp.com)<br>Aegis offers custom engineering and technology solutions to various clients, focusing on multi-disciplined approaches, hardware and software testing, and GIS-based mobile solutions | IT Services and IT Consulting | 🇺🇸 Seattle | 3,156 | 1995 |
| 6 | [Zones, LLC](https://www.tamtam.ai/c/zones-llc) (zones.com)<br>Global IT solution provider with expertise in digital workplace, cloud services, networking, security, and staffing solutions Operating in 120+ countries with top certifications | IT Services and IT Consulting | 🇺🇸 Auburn | 3,134 | 1986 |
| 7 | [Perkins Coie](https://www.tamtam.ai/c/perkins-coie) (perkinscoie.com)<br>Providing comprehensive legal advice in corporate, litigation, intellectual property, and regulatory matters to innovative companies and organizations worldwide. | Law Practice | 🇺🇸 Seattle | 2,815 | 1912 |
| 8 | [NAES](https://www.tamtam.ai/c/naes) (naes.com)<br>A leading provider of operations, maintenance, construction, engineering and technical services for power generation industry, prioritizing safety, compliance, quality, and integrity | Utilities | 🇺🇸 Issaquah | 2,309 | 1980 |
| 9 | [McKinstry](https://www.tamtam.ai/c/mckinstry) (mckinstry.com)<br>A national construction and energy services firm focused on eliminating waste and reducing climate impact in the built environment through innovation | Construction | 🇺🇸 Seattle | 2,295 | 1960 |
| 10 | [MAQ Software](https://www.tamtam.ai/c/maq-software) (maqsoftware.com)<br>A leading provider of business intelligence and analytics solutions, specializing in Microsoft Power BI, with a focus on accelerating productivity and fostering customer relationships | IT Services and IT Consulting | 🇺🇸 Redmond | 2,145 | 2000 |
| 11 | [People Tech Group Inc](https://www.tamtam.ai/c/people-tech-group-inc) (questglobal.com)<br>Leading provider of Enterprise Solutions, Digital Transformation, Data Intelligence, and Modern Operation services for small to large enterprises and Fortune 500 clients | IT Services and IT Consulting | 🇺🇸 Redmond | 2,026 | 2006 |
| 12 | [Russell Investments](https://www.tamtam.ai/c/russell-investments) (bit.ly)<br>Providing diverse investment capabilities and solutions to institutional, financial intermediaries, and individual investors worldwide, enhancing financial security. | Financial Services | 🇺🇸 Seattle | 2,004 | 1936 |
| 13 | [Moss Adams](https://www.tamtam.ai/c/moss-adams) (bakertilly.com)<br>Provides accounting, tax, and advisory services with extensive industry insights and holistic solutions for middle market businesses nationwide. | Accounting | 🇺🇸 Seattle | 2,001 | 1913 |
| 14 | [BBSI](https://www.tamtam.ai/c/bbsi) (bbsi.com)<br>A PEO providing HR, payroll, workers' comp, benefits, and consulting services through a local support model to small and medium-sized businesses | Human Resources Services | 🇺🇸 Vancouver | 1,899 | 1972 |
| 15 | [Wicresoft](https://www.tamtam.ai/c/wicresoft) (wicresoftinternational.com)<br>This company offers advisory, solution development, and operational support in areas such as talent acquisition, IT infrastructure, telecom services, and cloud solutions for Fortune 500 companies | Business Consulting and Services | 🇺🇸 Bellevue | 1,894 | 2002 |
| 16 | [POP](https://www.tamtam.ai/c/pop) (wearepop.com)<br>A digitally-focused agency that designs campaigns and technology platforms, prioritizing customer data to form partnerships with global brands | Advertising Services | 🇺🇸 Seattle | 1,868 | 1996 |
| 17 | [We. Communications](https://www.tamtam.ai/c/we-communications) (wecommunications.com)<br>Global communications agency translating technology innovations into meaningful experiences, helping brands connect with diverse audiences and navigate complex changes. | Public Relations and Communications Services | 🇺🇸 Bellevue | 1,791 |  |
| 18 | [iLink Digital](https://www.tamtam.ai/c/ilink-digital) (ilink-digital.com)<br>Helps enterprises move from AI ambition to AI reality with data foundations, security posture, cloud infrastructure, and intelligent applications. | IT Services and IT Consulting | 🇺🇸 Bothell | 1,789 | 2002 |
| 19 | [Lighthouse](https://www.tamtam.ai/c/lighthouse-seattle) (lighthouseglobal.com)<br>This company simplifies ediscovery and governance with intuitive technology solutions and services, guiding clients with expertise and proactive support globally | Legal Services | 🇺🇸 Seattle | 1,730 | 1995 |
| 20 | [Slalom Build](https://www.tamtam.ai/c/slalom-build) (slalombuild.com)<br>This company provides end-to-end solutions for clients in strategy, technology, product creation, and workforce modernization, building modern technology products with courage and innovation | IT Services and IT Consulting | 🇺🇸 Seattle | 1,577 |  |
| 21 | [KPFF Consulting Engineers](https://www.tamtam.ai/c/kpff-consulting-engineers) (kpff.com)<br>A multi-discipline engineering firm driven by core values, providing creative solutions for projects of all scales and industries for over 60 years | Professional Services | 🇺🇸 Seattle | 1,504 | 1960 |
| 22 | [Ro Health](https://www.tamtam.ai/c/ro-health) (rohealth.com)<br>A healthcare staffing agency prioritizing provider and client needs with innovative technology for efficient and quality patient care solutions | Staffing and Recruiting | 🇺🇸 Seattle | 1,354 | 2013 |
| 23 | [Aditi Consulting](https://www.tamtam.ai/c/aditi-consulting) (aditiconsulting.com)<br>A consultancy that connects talent, teams, and technology solutions to accelerate clients' digital journey through unique experiences and customized solutions | IT Services and IT Consulting | 🇺🇸 Bellevue | 1,236 | 1994 |
| 24 | [Tegria](https://www.tamtam.ai/c/tegria) (tegria.com)<br>Tegria offers consulting and technology solutions for healthcare organizations to enhance technology, operations, finances, and care quality Learn more at wwwtegriacom | IT Services and IT Consulting | 🇺🇸 Spokane | 1,167 | 2020 |
| 25 | [Applexus Technologies](https://www.tamtam.ai/c/applexus-technologies) (applexus.com)<br>Global leader in business consulting and SAP services, specializing in SAP S/4HANA and B/4HANA solutions across various industries worldwide | IT Services and IT Consulting | 🇺🇸 Federal Way | 1,138 | 2005 |
| 26 | [Kidder Mathews](https://www.tamtam.ai/c/kidder-mathews) (kidder.com)<br>Trusted independent counsel and expertise in commercial real estate, with over 50 years of experience and a wide range of services offered | Real Estate | 🇺🇸 Seattle | 1,061 | 1969 |
| 27 | [Stantec Consulting](https://www.tamtam.ai/c/stantec-consulting) (stantec.com)<br>Professional consulting firm specializing in infrastructure planning, design, surveying, civil design, security planning, and construction services, with access to added expertise and resources | Civil Engineering | 🇺🇸 Bellevue | 972 |  |
| 28 | [MSV International, Inc.](https://www.tamtam.ai/c/msv-international-inc) (msvgroup.com)<br>A multidisciplinary consultancy firm with global presence, offering expertise in infrastructure projects and services to international clients worldwide | Civil Engineering | 🇺🇸 Kenmore | 966 | 2001 |
| 29 | [Pacific NorthWest Law Group](https://www.tamtam.ai/c/pacific-northwest-law-group) (pnwlg.com)<br>Providing quality legal services and innovative solutions to clients worldwide through experienced lawyers and staff in multiple locations | Law Practice | 🇺🇸 Redmond | 934 |  |
| 30 | [Harbinger Group](https://www.tamtam.ai/c/harbinger-group) (harbingergroup.com)<br>Global technology innovator in HR, eLearning, publishing, education, and high-tech sectors Specializing in product development, content services, and workforce transformation solutions | Software Development | 🇺🇸 Redmond | 915 | 1990 |
| 31 | [Parametrix](https://www.tamtam.ai/c/parametrix) (parametrix.com)<br>Parametrix helps clients envision sustainable and vibrant communities while delivering inspired solutions for complex infrastructure and environmental projects #IMAGINEParametrix | Civil Engineering | 🇺🇸 Seattle | 899 | 1969 |
| 32 | [NAC](https://www.tamtam.ai/c/nac-seattle) (nacarchitecture.com)<br>An award-winning design firm with expertise in education, healthcare, senior living, and community recreation, creating innovative spaces that enhance lives | Architecture and Planning | 🇺🇸 Seattle | 888 | 1960 |
| 33 | [ABC Legal Services](https://www.tamtam.ai/c/abc-legal-services) (abclegal.com)<br>Nationwide provider of legal process services, offering cloud-based platforms and connecting law firms with appearance counsel efficiently. | Legal Services | 🇺🇸 Seattle | 882 | 1974 |
| 34 | [Coffman Engineers](https://www.tamtam.ai/c/coffman-engineers) (coffman.com)<br>A multidisciplinary engineering firm offering services in commercial, retail, government, industrial, and project management sectors with a reputation for innovation and teamwork | Design Services | 🇺🇸 Seattle | 842 | 1979 |
| 35 | [NBBJ Design](https://www.tamtam.ai/c/nbbj-design) (nbbj.com)<br>An innovative architecture and design firm creating dynamic environments for industry leaders and institutions worldwide, with a focus on community connectivity and sustainability | Architecture and Planning | 🇺🇸 Seattle | 841 | 1943 |
| 36 | [Blueprint](https://www.tamtam.ai/c/blueprint) (bpcs.com)<br>A technology solutions firm focused on digital transformation in various industries, enhancing customer experience, supply chain efficiency, and overall productivity | IT Services and IT Consulting | 🇺🇸 Bellevue | 770 | 2013 |
| 37 | [IEH Laboratories and Consulting Group](https://www.tamtam.ai/c/ieh-laboratories-and-consulting-group) (iehinc.com)<br>International lab & consulting services provider for food industry Offering comprehensive testing, safety, compliance, and crisis management solutions across multiple countries | Biotechnology Research | 🇺🇸 Lake Forest Park | 706 | 2001 |
| 38 | [Point B](https://www.tamtam.ai/c/point-b) (pointb.com)<br>Consulting firm combining expertise, industry insight, and technology to solve challenges and deliver value through collaborative talent and technology integration. | Business Consulting and Services | 🇺🇸 Seattle | 706 | 1995 |
| 39 | [Confiz](https://www.tamtam.ai/c/confiz) (confiz.com)<br>A global provider of technology solutions and consulting services, helping Fortune 500 companies in various industries improve their digital infrastructure through innovative technology solutions | IT Services and IT Consulting | 🇺🇸 Bellevue | 656 | 2005 |
| 40 | [PeopleReady Skilled Trades](https://www.tamtam.ai/c/peopleready-skilled-trades) (skilled.peopleready.com)<br>Innovative company changing how people connect with work Join award-winning team with career opportunities Learn more at peoplereadycom/careers | Staffing and Recruiting | 🇺🇸 Tacoma | 571 |  |
| 41 | [DOWL](https://www.tamtam.ai/c/dowl) (dowl.com)<br>A leading engineering firm with a dedicated team providing planning, surveying, civil/transportation, environmental services, and more across the western region | Civil Engineering | 🇺🇸 Bellevue | 565 | 1962 |
| 42 | [Allyis](https://www.tamtam.ai/c/allyis) (allyis.com)<br>Provider of technology, consulting, and managed services in web development, SharePoint, project management, marketing, and business intelligence with emphasis on employee support and community | IT Services and IT Consulting | 🇺🇸 Kirkland | 564 | 1996 |
| 43 | [MG2 Design](https://www.tamtam.ai/c/mg2-design) (mg2.com)<br>Global architecture, design, construction, and branding studio creating innovative community environments, consumer experiences, and client programs while promoting social responsibility | Architecture and Planning | 🇺🇸 Seattle | 538 | 1971 |
| 44 | [Unify Technologies](https://www.tamtam.ai/c/unify-technologies) (unifytech.com)<br>An experienced digital engineering firm that assists global clients in rapidly and cost-effectively developing high-quality custom software products | Software Development | 🇺🇸 Bellevue | 527 | 2015 |
| 45 | [Anchor QEA](https://www.tamtam.ai/c/anchor-qea) (anchorqea.com)<br>An environmental science and engineering consulting firm specializing in aquatic, shoreline, and water resource projects, providing services nationwide | Environmental Services | 🇺🇸 Seattle | 526 | 1997 |
| 46 | [Relanto](https://www.tamtam.ai/c/relanto) (relanto.ai)<br>Global services partner for innovation, specializing in Data, AI, Automation, Planning, and Cloud Solutions, transforming possibilities into reality with technology expertise | Business Consulting and Services | 🇺🇸 Seattle | 517 | 2021 |
| 47 | [LaborWorks, Inc.](https://www.tamtam.ai/c/laborworks-inc) (laborworks.com)<br>National industrial staffing company providing quality solutions in four states Recognized for leadership, customer service, and recruiting screened workers Values respect, integrity, teamwork, and excellence | Staffing and Recruiting | 🇺🇸 Gig Harbor | 514 | 1998 |
| 48 | [Affine](https://www.tamtam.ai/c/affine) (affine.ai)<br>Leading consulting firm driving enterprise transformation with analytics, cloud migration, big data analytics, AI solutions, and deployment consulting for Fortune-500 global enterprises | Business Consulting and Services | 🇺🇸 Bellevue | 498 | 2011 |
| 49 | [BellMedEx Medical Billing and Revenue Cycle Management Services](https://www.tamtam.ai/c/bellmedex-medical-billing-and-revenue-cycle-management-services) (bellmedex.com)<br>A Seattle-based company provides Revenue Cycle Management services for medical practices nationwide, focusing on exceeding customer expectations and customized solutions | Hospitals and Health Care | 🇺🇸 Seattle | 497 |  |
| 50 | [Language Link - A BIG Language company](https://www.tamtam.ai/c/language-link-a-big-language-company) (language.link)<br>A language solutions company offering translation, interpretation, and localization services in over 240 languages with a network of professionals and advanced technology | Translation and Localization | 🇺🇸 Vancouver | 495 | 1991 |

## 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 Washington State

- [The largest companies in Washington State](https://www.tamtam.ai/l/largest-companies-washington-state) (2,143)
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## 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)
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- [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)
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- [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-washington-state