# The 30 largest professional services firms in Arlington
Tamtam tracks 44 professional services firms headquartered in Arlington. This list ranks the 30 largest by number of employees on LinkedIn, led by Accenture Federal Services, TSC and CNA Corporation. Their median headcount is 396. Half of them were founded in 2002 or later.
The professional services firms in Arlington are mostly mid-sized to large organizations, with a strong presence in IT services, research, and international development. Accenture Federal Services, with 9,719 employees, focuses on advanced R&D and technology for the federal government. CNA Corporation and American Institutes for Research are nonprofit research organizations specializing in national security and evidence-based solutions, respectively. DT Global works on sustainable development and peacebuilding.
A notable pattern among these companies is their focus on serving government and public sector clients, particularly in defense, national security, and federal agencies. Many firms, such as TSC, founded in 1966, and ANSER, founded in 1958, have long histories, indicating established expertise in their fields. There is also a cluster of IT consulting firms like CEB, now Gartner, and Tria Federal, providing digital transformation and advisory services.
๐บ๐ธ Arlington ยท 30 companies ยท Updated Nov 11, 2026
| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [Accenture Federal Services](https://www.tamtam.ai/c/accenture-federal-services) (accenture.com)
The company brings advanced R&D, latest technologies, and human-centered design to the federal government to create lasting value and drive positive change | IT Services and IT Consulting | ๐บ๐ธ Arlington | 9,719 | |
| 2 | [TSC](https://www.tamtam.ai/c/tsc-arlington) (tsc.com)
An employee-owned high-tech company providing engineering services and specialized products to US Government agencies and private industry, supporting system life cycle from concept development to operations | Defense and Space Manufacturing | ๐บ๐ธ Arlington | 2,526 | 1966 |
| 3 | [CNA Corporation](https://www.tamtam.ai/c/cna-corporation) (cna.org)
A nonprofit research organization focused on national security, providing actionable solutions to complex problems through data analysis and field programs | Research Services | ๐บ๐ธ Arlington | 2,094 | 1942 |
| 4 | [American Institutes for Research](https://www.tamtam.ai/c/american-institutes-for-research) (air.org)
A nonprofit research institution providing evidence-based solutions for urgent challenges in education, health, workforce, human services, and international development worldwide | Research Services | ๐บ๐ธ Arlington | 2,010 | 1946 |
| 5 | [CEB, now Gartner](https://www.tamtam.ai/c/ceb-now-gartner) (gartner.com)
Providing research, advisory services, and technology solutions to help organizations make informed decisions and achieve their strategic priorities for future success | IT Services and IT Consulting | ๐บ๐ธ Arlington | 1,934 | 1983 |
| 6 | [DT Global](https://www.tamtam.ai/c/dt-global) (dt-global.com)
An international organization focused on sustainable development, innovation, and solving complex problems in peacebuilding, governance, economic development, environment, and human development sectors | International Trade and Development | ๐บ๐ธ Arlington | 1,912 | 2019 |
| 7 | [Tria Federal (Tria)](https://www.tamtam.ai/c/tria-federal-tria) (triafed.com)
Provides digital transformation solutions and advisory services to federal health and public safety agencies, addressing capability gaps for faster, smarter operations. | IT Services and IT Consulting | ๐บ๐ธ Arlington | 1,412 | 2022 |
| 8 | [Deloitte](https://www.tamtam.ai/c/deloitte-arlington) (deloitte.com)
A global professional services organization specializing in consulting, financial advisory, risk management, tax, and auditing services for clients in various industries | Business Consulting and Services | ๐บ๐ธ Arlington | 1,383 | |
| 9 | [Management Systems International](https://www.tamtam.ai/c/management-systems-international) (msiworldwide.com)
An international development firm with a 30-year history, operating in challenging environments worldwide, employing 800 experts in public sector management and governance | International Trade and Development | ๐บ๐ธ Arlington | 706 | 1981 |
| 10 | [The Cadmus Group](https://www.tamtam.ai/c/the-cadmus-group) (cadmusgroup.com)
Global strategic consulting firm providing transformative digital solutions and expertise to help clients achieve goals and strengthen society and environment. | Business Consulting and Services | ๐บ๐ธ Arlington | 691 | |
| 11 | [ANSER](https://www.tamtam.ai/c/anser) (anser.org)
A public service research institute providing objective analysis in national security, homeland security, and public policy, specializing in technology development collaborations | Business Consulting and Services | ๐บ๐ธ Arlington | 633 | 1958 |
| 12 | [Lovelytics](https://www.tamtam.ai/c/lovelytics) (lovelytics.com)
Data and analytics consultancy specializing in delivering services, building solutions, and promoting self-sufficiency through hands-on enablement for individuals, teams, and organizations | Business Consulting and Services | ๐บ๐ธ Arlington | 626 | 2017 |
| 13 | [Ola Tax](https://www.tamtam.ai/c/ola-tax) (olatax.com)
Established in 2008, specializing in property tax appeals Provides representation from negotiations to hearings and even arbitration or litigation if needed, ensuring due process for clients | Real Estate | ๐บ๐ธ Arlington | 447 | 2008 |
| 14 | [MultiState](https://www.tamtam.ai/c/multistate) (multistate.us)
A full-service government relations company providing expertise in tracking issues, advocacy campaigns, lobbying, compliance, policy analysis, and advocacy plans | Government Relations Services | ๐บ๐ธ Arlington | 407 | 1984 |
| 15 | [Excella](https://www.tamtam.ai/c/excella) (excella.com)
Technology firm partnering with organizations to deliver collaborative, high-performing solutions that address critical challenges and empower mission success. | Technology, Information and Internet | ๐บ๐ธ Arlington | 396 | 2002 |
| 16 | [Leidos Gibbs & Cox](https://www.tamtam.ai/c/leidos-gibbs-and-cox) (gibbscox.com)
An engineering and design firm specializing in naval architecture, marine engineering, and consulting for government and commercial maritime programs | Maritime Transportation | ๐บ๐ธ Arlington | 396 | 1929 |
| 17 | [Technomics, Inc.](https://www.tamtam.ai/c/technomics-inc) (technomics.net)
A growing consulting firm specializes in weapon system cost analysis, providing unbiased analysis and advice to assist clients in making critical decisions efficiently | Defense and Space Manufacturing | ๐บ๐ธ Arlington | 377 | 1984 |
| 18 | [Piedmont Global](https://www.tamtam.ai/c/piedmont-global) (piedmontglobal.com)
A leading provider of Translation, Interpretation, and Language Training solutions in over 200 languages, advancing global missions of partners | Strategic Management Services | ๐บ๐ธ Arlington | 374 | 2013 |
| 19 | [Hanover Research](https://www.tamtam.ai/c/hanover-research) (hanoverresearch.com)
Provides custom market research and analytics using diverse methodologies, delivering strategic insights to organizations with flexible, fixed-fee service model. | Market Research | ๐บ๐ธ Arlington | 364 | 2003 |
| 20 | [FCi Federal](https://www.tamtam.ai/c/fci-federal) (amentum.com)
A company providing federal services has joined PAE, now connecting through LinkedIn at wwwlinkedincom/company/pae | Government Administration | ๐บ๐ธ Arlington | 362 | 1991 |
| 21 | [Fors Marsh](https://www.tamtam.ai/c/fors-marsh) (forsmarsh.com)
A purpose-driven firm specializing in behavioral research and strategy to solve complex problems and drive lasting change in key markets | Business Consulting and Services | ๐บ๐ธ Arlington | 350 | 2002 |
| 22 | [Innovative Driven](https://www.tamtam.ai/c/innovative-driven) (innovativedriven.com)
Innovative Driven maximizes business success by turning data into an asset and ensuring proper management and protection of information through technology and industry best practices | Legal Services | ๐บ๐ธ Arlington | 346 | 2005 |
| 23 | [Millennium](https://www.tamtam.ai/c/millennium-arlington) (millgroupinc.com)
A cybersecurity company with over 400 experts specializing in Red Team Operations, Defensive Cyber Operations, Software Engineering, and Technical Engineering | IT Services and IT Consulting | ๐บ๐ธ Arlington | 346 | 2004 |
| 24 | [Eagle Hill Consulting](https://www.tamtam.ai/c/eagle-hill-consulting) (eaglehillconsulting.com)
A woman-owned, award-winning management consulting firm delivering innovative solutions in Strategy, Talent, and Change across various sectors with exceptional delivery and culture | Business Consulting and Services | ๐บ๐ธ Arlington | 329 | 2003 |
| 25 | [cBEYONData + SMX](https://www.tamtam.ai/c/cbeyondata-smx) (cbeyondata.com)
Specializing in business process enhancement, cloud migration, BI, data management, analytics, project management, and financial reporting solutions for mission-driven agencies and organizations | IT Services and IT Consulting | ๐บ๐ธ Arlington | 314 | 2011 |
| 26 | [540](https://www.tamtam.ai/c/540-arlington) (540.co)
A technology consulting firm specializing in helping government and business clients innovate with tech strategy, software development, API design/dev, and DevOps services | IT Services and IT Consulting | ๐บ๐ธ Arlington | 288 | 2013 |
| 27 | [Falconwood, Incorporated](https://www.tamtam.ai/c/falconwood-incorporated) (falconwood.biz)
A small, woman-owned business offering executive consultants and program support for Department of Defense IT initiatives, specializing in acquisition strategy and Information Assurance | Defense and Space Manufacturing | ๐บ๐ธ Arlington | 248 | 2002 |
| 28 | [Aperture LLC](https://www.tamtam.ai/c/aperture-llc) (aperturellc.com)
A national portfolio of forensic engineering companies that provide expert analysis to uncover truth and improve the world through science | Legal Services | ๐บ๐ธ Arlington | 245 | 2019 |
| 29 | [Source Advisors](https://www.tamtam.ai/c/source-advisors) (sourceadvisors.com)
Specialized tax consulting firm providing R&D Tax Credit, Cost Segregation, Energy Efficiency, and LIFO inventory solutions for over 40 years | Financial Services | ๐บ๐ธ Arlington | 213 | 1983 |
| 30 | [Dexis](https://www.tamtam.ai/c/dexis-arlington) (dexisonline.com)
Global professional services firm dedicated to working with leaders and communities to create a safe, just, and prosperous world | Professional Services | ๐บ๐ธ Arlington | 202 | 2001 |
## 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 Arlington
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- [Multinational companies in Arlington](https://www.tamtam.ai/l/multinational-companies-arlington) (71)
- [Aerospace and defence companies in Arlington](https://www.tamtam.ai/l/aerospace-and-defense-companies-arlington) (46)
- [Consulting firms in Arlington](https://www.tamtam.ai/l/consulting-firms-arlington) (44)
- [IT Services and IT Consulting companies in Arlington](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-arlington) (41)
- [Companies with in-house R&D in Arlington](https://www.tamtam.ai/l/r-and-d-companies-arlington) (39)
- [IT services companies in Arlington](https://www.tamtam.ai/l/it-services-companies-arlington) (33)
- [Non-profit Organizations companies in Arlington](https://www.tamtam.ai/l/non-profit-organizations-companies-arlington) (32)
- [Manufacturers in Arlington](https://www.tamtam.ai/l/manufacturers-arlington) (27)
## 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 California](https://www.tamtam.ai/l/professional-services-firms-california) (880)
- [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)
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Source: https://www.tamtam.ai/l/professional-services-firms-arlington