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.
| # | Company | Employees | |||
|---|---|---|---|---|---|
| 1 |
Avanadeavanade.com
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 |
50,000 | |||
| 2 | 20,860 | ||||
| 3 |
TrueBlue Inc.trueblue.com
Staffing, recruiting, and workforce management services for diverse industries, providing reliable and efficient workforce solutions daily. |
12,447 | |||
| 4 |
Slalomslalom.com
Consulting firm delivering strategy, technology, and data-driven solutions to improve operations, customer experiences, and sustainable growth globally. |
10,268 | |||
| 5 |
Aegisaegisgrp.com
Aegis offers custom engineering and technology solutions to various clients, focusing on multi-disciplined approaches, hardware and software testing, and GIS-based mobile solutions |
3,156 | |||
| 6 |
Zones, LLCzones.com
Global IT solution provider with expertise in digital workplace, cloud services, networking, security, and staffing solutions Operating in 120+ countries with top certifications |
3,134 | |||
| 7 |
Perkins Coieperkinscoie.com
Providing comprehensive legal advice in corporate, litigation, intellectual property, and regulatory matters to innovative companies and organizations worldwide. |
2,815 | |||
| 8 | 2,309 | ||||
| 9 |
McKinstrymckinstry.com
A national construction and energy services firm focused on eliminating waste and reducing climate impact in the built environment through innovation |
2,295 | |||
| 10 |
MAQ Softwaremaqsoftware.com
A leading provider of business intelligence and analytics solutions, specializing in Microsoft Power BI, with a focus on accelerating productivity and fostering customer relationships |
2,145 | |||
| 11 |
People Tech Group Incquestglobal.com
Leading provider of Enterprise Solutions, Digital Transformation, Data Intelligence, and Modern Operation services for small to large enterprises and Fortune 500 clients |
2,026 | |||
| 12 |
Russell Investmentsbit.ly
Providing diverse investment capabilities and solutions to institutional, financial intermediaries, and individual investors worldwide, enhancing financial security. |
2,004 | |||
| 13 |
Moss Adamsbakertilly.com
Provides accounting, tax, and advisory services with extensive industry insights and holistic solutions for middle market businesses nationwide. |
2,001 | |||
| 14 | 1,899 | ||||
| 15 |
Wicresoftwicresoftinternational.com
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 |
1,894 | |||
| 16 |
POPwearepop.com
A digitally-focused agency that designs campaigns and technology platforms, prioritizing customer data to form partnerships with global brands |
1,868 | |||
| 17 |
We. Communicationswecommunications.com
Global communications agency translating technology innovations into meaningful experiences, helping brands connect with diverse audiences and navigate complex changes. |
1,791 | |||
| 18 |
iLink Digitalilink-digital.com
Helps enterprises move from AI ambition to AI reality with data foundations, security posture, cloud infrastructure, and intelligent applications. |
1,789 | |||
| 19 |
Lighthouselighthouseglobal.com
This company simplifies ediscovery and governance with intuitive technology solutions and services, guiding clients with expertise and proactive support globally |
1,730 | |||
| 20 |
Slalom Buildslalombuild.com
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 |
1,577 | |||
| 21 |
KPFF Consulting Engineerskpff.com
A multi-discipline engineering firm driven by core values, providing creative solutions for projects of all scales and industries for over 60 years |
1,504 | |||
| 22 |
Ro Healthrohealth.com
A healthcare staffing agency prioritizing provider and client needs with innovative technology for efficient and quality patient care solutions |
1,354 | |||
| 23 |
Aditi Consultingaditiconsulting.com
A consultancy that connects talent, teams, and technology solutions to accelerate clients' digital journey through unique experiences and customized solutions |
1,236 | |||
| 24 |
Tegriategria.com
Tegria offers consulting and technology solutions for healthcare organizations to enhance technology, operations, finances, and care quality Learn more at wwwtegriacom |
1,167 | |||
| 25 |
Applexus Technologiesapplexus.com
Global leader in business consulting and SAP services, specializing in SAP S/4HANA and B/4HANA solutions across various industries worldwide |
1,138 | |||
Want more companies than this list?This page shows the largest ones only. Connect to Tamtam to see every company that matches, filter by size, industry or growth, and reach their decision-makers. | |||||
| 26 |
Kidder Mathewskidder.com
Trusted independent counsel and expertise in commercial real estate, with over 50 years of experience and a wide range of services offered |
1,061 | |||
| 27 |
Stantec Consultingstantec.com
Professional consulting firm specializing in infrastructure planning, design, surveying, civil design, security planning, and construction services, with access to added expertise and resources |
972 | |||
| 28 |
MSV International, Inc.msvgroup.com
A multidisciplinary consultancy firm with global presence, offering expertise in infrastructure projects and services to international clients worldwide |
966 | |||
| 29 |
Pacific NorthWest Law Grouppnwlg.com
Providing quality legal services and innovative solutions to clients worldwide through experienced lawyers and staff in multiple locations |
934 | |||
| 30 |
Harbinger Groupharbingergroup.com
Global technology innovator in HR, eLearning, publishing, education, and high-tech sectors Specializing in product development, content services, and workforce transformation solutions |
915 | |||
| 31 |
Parametrixparametrix.com
Parametrix helps clients envision sustainable and vibrant communities while delivering inspired solutions for complex infrastructure and environmental projects #IMAGINEParametrix |
899 | |||
| 32 |
NACnacarchitecture.com
An award-winning design firm with expertise in education, healthcare, senior living, and community recreation, creating innovative spaces that enhance lives |
888 | |||
| 33 |
ABC Legal Servicesabclegal.com
Nationwide provider of legal process services, offering cloud-based platforms and connecting law firms with appearance counsel efficiently. |
882 | |||
| 34 |
Coffman Engineerscoffman.com
A multidisciplinary engineering firm offering services in commercial, retail, government, industrial, and project management sectors with a reputation for innovation and teamwork |
842 | |||
| 35 |
NBBJ Designnbbj.com
An innovative architecture and design firm creating dynamic environments for industry leaders and institutions worldwide, with a focus on community connectivity and sustainability |
841 | |||
| 36 | 770 | ||||
| 37 |
IEH Laboratories and Consulting Groupiehinc.com
International lab & consulting services provider for food industry Offering comprehensive testing, safety, compliance, and crisis management solutions across multiple countries |
706 | |||
| 38 |
Point Bpointb.com
Consulting firm combining expertise, industry insight, and technology to solve challenges and deliver value through collaborative talent and technology integration. |
706 | |||
| 39 |
Confizconfiz.com
A global provider of technology solutions and consulting services, helping Fortune 500 companies in various industries improve their digital infrastructure through innovative technology solutions |
656 | |||
| 40 |
PeopleReady Skilled Tradesskilled.peopleready.com
Innovative company changing how people connect with work Join award-winning team with career opportunities Learn more at peoplereadycom/careers |
571 | |||
| 41 | 565 | ||||
| 42 |
Allyisallyis.com
Provider of technology, consulting, and managed services in web development, SharePoint, project management, marketing, and business intelligence with emphasis on employee support and community |
564 | |||
| 43 |
MG2 Designmg2.com
Global architecture, design, construction, and branding studio creating innovative community environments, consumer experiences, and client programs while promoting social responsibility |
538 | |||
| 44 |
Unify Technologiesunifytech.com
An experienced digital engineering firm that assists global clients in rapidly and cost-effectively developing high-quality custom software products |
527 | |||
| 45 |
Anchor QEAanchorqea.com
An environmental science and engineering consulting firm specializing in aquatic, shoreline, and water resource projects, providing services nationwide |
526 | |||
| 46 |
Relantorelanto.ai
Global services partner for innovation, specializing in Data, AI, Automation, Planning, and Cloud Solutions, transforming possibilities into reality with technology expertise |
517 | |||
| 47 |
LaborWorks, Inc.laborworks.com
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 |
514 | |||
| 48 | 498 | ||||
| 49 |
BellMedEx Medical Billing and Revenue Cycle Management Servicesbellmedex.com
A Seattle-based company provides Revenue Cycle Management services for medical practices nationwide, focusing on exceeding customer expectations and customized solutions |
497 | |||
| 50 |
Language Link - A BIG Language companylanguage.link
A language solutions company offering translation, interpretation, and localization services in over 240 languages with a network of professionals and advanced technology |
495 | |||
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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 2,143
- Multinational companies in Washington State 288
- Manufacturers in Washington State 176
- Education providers in Washington State 169
- Retail chains in Washington State 161
- IT Services and IT Consulting companies in Washington State 160
- SaaS companies in Washington State 155
- Critical infrastructure operators in Washington State 149
- IT services companies in Washington State 145
- Companies with in-house R&D in Washington State 140
- Software Development companies in Washington State 140
- Public sector organisations in Washington State 139
- Healthcare providers in Washington State 136
- Companies with a mobile app in Washington State 128
- Hardware manufacturers in Washington State 121
- AI companies in Washington State 110
- Hospitals and Health Care companies in Washington State 107
- Consulting firms in Washington State 106
- Financial services firms in Washington State 92
- Construction companies in Washington State 87
- Subscription businesses in Washington State 86
- Higher Education companies in Washington State 74
- Family-owned companies in Washington State 73
- E-commerce companies in Washington State 69
The same list elsewhere in United States
- Professional services firms in the United States 7,078
- Professional services firms in New York State 955
- Professional services firms in California 880
- Professional services firms in Texas 629
- Professional services firms in Florida 375
- Professional services firms in Virginia 344
- Professional services firms in Illinois 339
- Professional services firms in Massachusetts 249
- Professional services firms in New Jersey 249
- Professional services firms in Georgia 246
- Professional services firms in Pennsylvania 245
- Professional services firms in Ohio 195
- Professional services firms in Maryland 176
- Professional services firms in Michigan 172
- Professional services firms in North Carolina 142
- Professional services firms in Alabama 135
- Professional services firms in Minnesota 125
- Professional services firms in New York 735
- Professional services firms in Chicago 196
- Professional services firms in Houston 156
- Professional services firms in Atlanta 143
- Professional services firms in San Francisco 130
- Professional services firms in Washington 109
- Professional services firms in Los Angeles 108