# The 50 largest professional services firms in Maryland

Tamtam tracks 176 professional services firms headquartered in Maryland. This list ranks the 50 largest by number of employees on LinkedIn, led by TEKsystems, Aerotek and Amergis Healthcare Staffing. Their median headcount is 1,371. Half of them were founded in 1988 or later. The most common headquarters are Rockville (10), Bethesda (7) and Hanover (6).

These professional services firms in Maryland are mostly large companies, many of them in staffing and IT services. TEKsystems is a global solutions provider specializing in IT, business, and talent challenges. Aerotek and Amergis Healthcare Staffing provide staffing solutions, while Actalent offers scalable talent solutions and services. GP Strategies Corporation focuses on consulting, learning services, and technology solutions, and Abt Global leads in research, evaluation, and program implementation.

A notable pattern among these companies is the concentration of headquarters in Hanover, with Allegis Group, TEKsystems, Aerotek, Actalent, and Aston Carter all based there. This suggests a cluster of talent and IT services within the region, with many firms founded between the 1980s and early 2000s.

🇺🇸 Maryland · 50 companies · Updated Nov 11, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [TEKsystems](https://www.tamtam.ai/c/teksystems) (teksystems.com)<br>Global solutions provider specializing in accelerating business transformation through resolving technology, business, and talent challenges for Fortune 500 organizations | IT Services and IT Consulting | 🇺🇸 Hanover | 28,131 | 1983 |
| 2 | [Aerotek](https://www.tamtam.ai/c/aerotek) (aerotek.com)<br>Aerotek provides staffing and services solutions for various industries, helping companies and careers evolve to overcome challenges in North American industry | Staffing and Recruiting | 🇺🇸 Hanover | 20,490 | 1983 |
| 3 | [Amergis Healthcare Staffing](https://www.tamtam.ai/c/amergis-healthcare-staffing) (amergis.com)<br>Healthcare staffing agency offering opportunities and solutions for various healthcare professionals and organizations with a personalized approach and exceptional service | Staffing and Recruiting | 🇺🇸 Columbia | 19,829 | 1988 |
| 4 | [Actalent](https://www.tamtam.ai/c/actalent) (actalentservices.com)<br>Actalent specializes in providing scalable talent solutions and services globally, focusing on engineering, sciences, and professional development to drive value for clients | Business Consulting and Services | 🇺🇸 Hanover | 6,572 |  |
| 5 | [GP Strategies Corporation](https://www.tamtam.ai/c/gp-strategies-corporation) (gpstrategies.com)<br>Provides consulting, learning services, and technology solutions to help organizations improve workforce performance and achieve business transformation through people. | Business Consulting and Services | 🇺🇸 Columbia | 4,090 | 1966 |
| 6 | [Abt Global](https://www.tamtam.ai/c/abt-global) (abtglobal.com)<br>Global leader in research, evaluation, and program implementation addressing health, education, environment, agriculture, housing, and data collection challenges worldwide. | Professional Services | 🇺🇸 Rockville | 3,748 |  |
| 7 | [DAI](https://www.tamtam.ai/c/dai) (dai.com)<br>A global development company with over 50 years of experience tackling social and economic challenges through innovative solutions in nearly 100 countries | International Trade and Development | 🇺🇸 Bethesda | 3,623 | 1970 |
| 8 | [Allegis Group](https://www.tamtam.ai/c/allegis-group) (allegisgroup.com)<br>Providing comprehensive talent solutions worldwide through specialized companies, connecting people with opportunities and solving workforce challenges for business success. | Staffing and Recruiting | 🇺🇸 Hanover | 3,570 | 1983 |
| 9 | [Precision Medicine Group](https://www.tamtam.ai/c/precision-medicine-group) (precisionmedicinegrp.com)<br>A company founded in 2012 focused on improving the drug development process through technology, data, human expertise, and strategic acquisitions | Pharmaceutical Manufacturing | 🇺🇸 Bethesda | 3,553 | 2012 |
| 10 | [Westat](https://www.tamtam.ai/c/westat) (westat.com)<br>Westat provides professional services to improve outcomes in health, education, social policy, and transportation through research, data collection, clinical trials, evaluation, and communication | Research Services | 🇺🇸 Bethesda | 3,419 | 1963 |
| 11 | [HealthPRO Heritage](https://www.tamtam.ai/c/healthpro-heritage) (healthpro-heritage.com)<br>A privately owned consulting and therapy management firm offering innovative, evidence-based therapy and wellness services for seniors across various care settings | Hospitals and Health Care | 🇺🇸 Hunt Valley | 3,109 | 1997 |
| 12 | [Allegis Global Solutions](https://www.tamtam.ai/c/allegis-global-solutions) (allegisglobalsolutions.com)<br>Global workforce solutions provider specializing in workforce design, management, consulting, and procurement to transform organizations and enhance competitive advantage. | Staffing and Recruiting | 🇺🇸 Hanover | 3,021 | 2001 |
| 13 | [KCI](https://www.tamtam.ai/c/kci) (kci.com)<br>Employee-owned engineering firm providing multi-disciplined services in transportation, resource management, environmental, and construction to government, institutional, and private-sector clients nationwide | Engineering Services | 🇺🇸 Sparks | 2,900 | 1955 |
| 14 | [Aston Carter](https://www.tamtam.ai/c/aston-carter) (astoncarter.com)<br>Providing specialized talent solutions in accounting, finance, HR, procurement, and supply chain to global clients including Fortune 500 companies. | Staffing and Recruiting | 🇺🇸 Hanover | 2,699 | 1997 |
| 15 | [RK&K](https://www.tamtam.ai/c/rk-and-k) (rkk.com)<br>A full-service firm offering planning, engineering, environmental, and construction management services, delivering creative solutions to improve communities and prioritizing collaboration and trust | Civil Engineering | 🇺🇸 Baltimore | 2,062 | 1923 |
| 16 | [Precision For Medicine](https://www.tamtam.ai/c/precision-for-medicine) (precisionformedicine.com)<br>A global precision medicine clinical research organization improving therapeutics development with integrated clinical operations, laboratory expertise, and advanced data sciences | Biotechnology Research | 🇺🇸 Bethesda | 2,060 |  |
| 17 | [The Henry M. Jackson Foundation for the Advancement of Military Medicine](https://www.tamtam.ai/c/the-henry-m-jackson-foundation-for-the-advancement-of-military-medicine) (hjf.org)<br>A nonprofit organization supporting military medical research, providing program management services to accelerate progress and advance Military Medicine | Research Services | 🇺🇸 Bethesda | 2,036 | 1983 |
| 18 | [SMX](https://www.tamtam.ai/c/smx) (smxtech.com)<br>A US based IT and engineering solutions provider specializing in Cloud Solutions, Cyber Security, Systems Integration, Data Analytics, and Mission-Focused Engineering | IT Services and IT Consulting | 🇺🇸 Hollywood | 1,934 | 1995 |
| 19 | [Jensen Hughes](https://www.tamtam.ai/c/jensen-hughes) (jensenhughes.com)<br>A global leader in fire protection engineering and risk management, offering expertise in safety and security consulting, emergency management, and digital innovation | Professional Services | 🇺🇸 Columbia | 1,851 |  |
| 20 | [Advarra](https://www.tamtam.ai/c/advarra) (advarra.com)<br>Advarra enhances clinical research by providing IRB and IBC review solutions, innovative technologies, and industry connections to optimize trial participant safety and research performance | Research Services | 🇺🇸 Columbia | 1,839 | 1983 |
| 21 | [Apex Companies](https://www.tamtam.ai/c/apex-companies-rockville) (apexcos.com)<br>A national consulting and engineering firm tackling environmental challenges, delivering real-time results, with a diverse team promoting exceptional client satisfaction | Professional Services | 🇺🇸 Rockville | 1,729 | 1988 |
| 22 | [Hughes Systique Corporation (HSC)](https://www.tamtam.ai/c/hughes-systique-corporation-hsc) (hsc.com)<br>A multinational provider of digital solutions and services, specializing in software development, with expertise in Networking, AI & ML, Retail, Automotive, IoT, Blockchain, and Security | Software Development | 🇺🇸 Rockville | 1,547 | 2005 |
| 23 | [Walker & Dunlop](https://www.tamtam.ai/c/walker-and-dunlop) (walkerdunlop.com)<br>Creating communities with ideas and capital, specializing in commercial real estate finance and advisory services for living, working, shopping, and playing | Financial Services | 🇺🇸 Bethesda | 1,493 |  |
| 24 | [Emmes Group](https://www.tamtam.ai/c/emmes-group) (theemmesgroup.com)<br>A company dedicated to advancing public health and biopharmaceutical innovation by combining human intelligence with artificial intelligence in clinical research | Research Services | 🇺🇸 Rockville | 1,411 | 2024 |
| 25 | [TBC](https://www.tamtam.ai/c/tbc-baltimore) (tbc.us)<br>An independent branding, advertising, and PR agency specializing in driving results through creative advertising, digital strategy, video production, and media planning | Marketing Services | 🇺🇸 Baltimore | 1,371 | 1974 |
| 26 | [Automotive Training Institute](https://www.tamtam.ai/c/automotive-training-institute) (autotraining.net)<br>Leading coaching and consulting company for auto repair and collision shops, helping owners improve business, achieve goals, and drive profits | Business Consulting and Services | 🇺🇸 Linthicum Heights | 1,351 |  |
| 27 | [Emmes](https://www.tamtam.ai/c/emmes) (theemmesgroup.com)<br>A global Contract Research Organization (CRO) with expertise in clinical research across various therapeutic areas, supporting public health and biopharmaceutical innovation | Research Services | 🇺🇸 Rockville | 1,188 |  |
| 28 | [Infosys Public Services](https://www.tamtam.ai/c/infosys-public-services) (infosyspublicservices.com)<br>Leader in business consulting, technology solutions, and digital services for public sector organizations in the US and Canada Specializes in digital transformation through experience, technology, innovation, and delivery excellence | IT Services and IT Consulting | 🇺🇸 Rockville | 1,125 | 2009 |
| 29 | [Brown Advisory](https://www.tamtam.ai/c/brown-advisory) (brownadvisory.com)<br>Independent firm providing investment management, strategic advice, and client service to individuals, families, institutions, and financial intermediaries worldwide. | Financial Services | 🇺🇸 Baltimore | 1,124 | 1993 |
| 30 | [URC](https://www.tamtam.ai/c/urc) (urc-chs.com)<br>Global company improving quality of health care, social services, and education through innovative, evidence-based solutions in over 30 countries | International Trade and Development | 🇺🇸 Chevy Chase | 1,068 | 1965 |
| 31 | [The MIL Corporation](https://www.tamtam.ai/c/the-mil-corporation) (milcorp.com)<br>A provider of cyber, engineering, financial, and information technology services to the federal government, emphasizing excellence, long-term relationships, and proven client retention | IT Services and IT Consulting | 🇺🇸 Bowie | 951 | 1980 |
| 32 | [EA Engineering, Science, and Technology, Inc., PBC](https://www.tamtam.ai/c/ea-engineering-science-and-technology-inc-pbc) (eaest.com)<br>An employee-owned public benefit corporation providing environmental, compliance, natural resources, and infrastructure engineering and management solutions to public and private clients nationwide | Environmental Services | 🇺🇸 Hunt Valley | 880 | 1973 |
| 33 | [TAI](https://www.tamtam.ai/c/tai) (tai.inc)<br>A US-based company providing dependable Engineering, Management, and Technical Services to the industrial engineering industry for over 33 years, domestically and globally | Construction | 🇺🇸 Owings Mills | 847 | 1989 |
| 34 | [Arch Amenities Group](https://www.tamtam.ai/c/arch-amenities-group) (archamenity.com)<br>Arch Amenities Group creates bespoke, innovative spaces for partners to enhance well-being, offering memorable experiences through expertly crafted amenities and practical comforts | Wellness and Fitness Services | 🇺🇸 Rockville | 845 | 1973 |
| 35 | [Blend](https://www.tamtam.ai/c/blend-columbia) (blend360.com)<br>A premier AI services provider combining data science, technology, and human expertise to co-create impactful solutions for clients Unlocking value through innovation | Professional Services | 🇺🇸 Columbia | 823 | 2016 |
| 36 | [Precise Systems, Inc.](https://www.tamtam.ai/c/precise-systems-inc) (goprecise.com)<br>A professional services company specializing in supporting US Department of Defense programs through digital transformation, advanced engineering, IT solutions, and technical support | Defense and Space Manufacturing | 🇺🇸 Lexington Park | 816 | 1990 |
| 37 | [ASEC](https://www.tamtam.ai/c/asec) (asec-incorporated.com)<br>ASEC is an engineering services firm specializing in aviation system development, analysis, test, and commercial drone operations for military and commercial clients | Aviation and Aerospace Component Manufacturing | 🇺🇸 Lexington Park | 812 | 2004 |
| 38 | [EEI Corporation](https://www.tamtam.ai/c/eei-corporation) (eeicorp.com)<br>EEI Corporation provides Environmental, Energy, Safety, Industrial Hygiene, and Security services globally, with expertise in auditing and federal contracts | Environmental Services | 🇺🇸 Rockville | 790 | 1995 |
| 39 | [Whitman, Requardt and Associates, LLP](https://www.tamtam.ai/c/whitman-requardt-and-associates-llp) (wrallp.com)<br>A nationally-recognized firm providing engineering, architectural, and environmental planning services with a focus on client service, quality work, and forward thinking solutions | Civil Engineering | 🇺🇸 Baltimore | 785 | 1915 |
| 40 | [Smartlink Group](https://www.tamtam.ai/c/smartlink-group) (smartlinkgroup.com)<br>A national talent solutions and telecom services company specializing in the development, engineering, and maintenance of communication infrastructures for leading wireless carriers and providers | Telecommunications | 🇺🇸 Annapolis | 704 | 2000 |
| 41 | [Abacus Technology Corporation](https://www.tamtam.ai/c/abacus-technology-corporation) (abacustech.com)<br>delivers high-quality assistance for complex technology challenges, offering innovative solutions to improve customer productivity with cost-effective information technology, engineering analysis, and enterprise management services. | IT Services and IT Consulting | 🇺🇸 Chevy Chase | 700 | 1983 |
| 42 | [Offit Kurman](https://www.tamtam.ai/c/offit-kurman) (offitkurman.com)<br>Full-service law firm specializing in 30+ areas of practice, providing innovative counsel to businesses, individuals, and families to maximize and protect value | Law Practice | 🇺🇸 Bethesda | 676 | 1987 |
| 43 | [ATS](https://www.tamtam.ai/c/ats-cambridge) (ats-business.com)<br>A global company with 30+ years of experience serving numerous clients, delivering exceptional results worth billions of dollars through best-in-class experts Visit https://wwwats-businesscom | Business Consulting and Services | 🇺🇸 Cambridge | 668 | 1980 |
| 44 | [CriticalRiver Inc.](https://www.tamtam.ai/c/criticalriver-inc) (criticalriver.com)<br>Provides comprehensive technology consulting, implementation, and managed services, leveraging digital transformation, cloud, and intelligent automation solutions for various industries to enhance operational efficiencies. | IT Services and IT Consulting | 🇺🇸 Pleasanton | 668 | 2014 |
| 45 | [Ad Astra, Inc.](https://www.tamtam.ai/c/ad-astra-inc) (ad-astrainc.com)<br>Global communication solutions and language services provider leveraging human expertise and technology to bridge linguistic divides for diverse industries | Translation and Localization | 🇺🇸 Silver Spring | 646 | 2010 |
| 46 | [The BOSS Group](https://www.tamtam.ai/c/the-boss-group) (cellainc.com)<br>A leader in creative, marketing, and digital staffing, with 30 years of experience and multiple award-winning recognition for talent and client satisfaction | Staffing and Recruiting | 🇺🇸 Rockville | 646 | 1988 |
| 47 | [Creative Associates International](https://www.tamtam.ai/c/creative-associates-international) (creativeassociatesinternational.com)<br>A social impact organization providing development services and partnerships to address global challenges in education, economic growth, governance, and conflict resolution | Professional Services | 🇺🇸 Chevy Chase | 597 | 1977 |
| 48 | [Science Systems and Applications, Inc (SSAI)](https://www.tamtam.ai/c/science-systems-and-applications-inc-ssai) (ssaihq.com)<br>Leading provider of science, engineering, and technology solutions supporting pioneers in Earth and space science missions with innovative research and technical support | Defense and Space Manufacturing | 🇺🇸 Lanham | 593 | 1977 |
| 49 | [TISTA Science and Technology Corporation](https://www.tamtam.ai/c/tista-science-and-technology-corporation) (tistatech.com)<br>IT and professional services provider for Federal, State, and commercial clients, specializing in cyber security, software development, engineering support, and IT operations | IT Services and IT Consulting | 🇺🇸 Rockville | 581 | 2005 |
| 50 | [Tech USA](https://www.tamtam.ai/c/tech-usa) (techusa.net)<br>A top-tier provider of staffing solutions specializing in IT, Engineering, Telecommunications, Scientific, and Government services Offers flexible workforce solutions and professional development opportunities | Staffing and Recruiting | 🇺🇸 Millersville | 580 | 1998 |

## 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 Maryland

- [The largest companies in Maryland](https://www.tamtam.ai/l/largest-companies-maryland) (1,688)
- [Multinational companies in Maryland](https://www.tamtam.ai/l/multinational-companies-maryland) (216)
- [IT Services and IT Consulting companies in Maryland](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-maryland) (189)
- [IT services companies in Maryland](https://www.tamtam.ai/l/it-services-companies-maryland) (179)
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- [Hospitals and Health Care companies in Maryland](https://www.tamtam.ai/l/hospitals-and-health-care-companies-maryland) (114)
- [Consulting firms in Maryland](https://www.tamtam.ai/l/consulting-firms-maryland) (112)
- [Companies with in-house R&D in Maryland](https://www.tamtam.ai/l/r-and-d-companies-maryland) (107)
- [Healthcare providers in Maryland](https://www.tamtam.ai/l/healthcare-providers-maryland) (105)
- [Critical infrastructure operators in Maryland](https://www.tamtam.ai/l/critical-infrastructure-operators-maryland) (94)
- [Retail chains in Maryland](https://www.tamtam.ai/l/retail-chains-maryland) (91)
- [Public sector organisations in Maryland](https://www.tamtam.ai/l/public-sector-organisations-maryland) (91)
- [Financial services firms in Maryland](https://www.tamtam.ai/l/financial-services-firms-maryland) (88)
- [Aerospace and defence companies in Maryland](https://www.tamtam.ai/l/aerospace-and-defense-companies-maryland) (80)
- [Construction companies in Maryland](https://www.tamtam.ai/l/construction-companies-maryland) (80)
- [Manufacturers in Maryland](https://www.tamtam.ai/l/manufacturers-maryland) (75)
- [Financial Services companies in Maryland](https://www.tamtam.ai/l/financial-services-companies-maryland) (65)
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- [Research institutes in Maryland](https://www.tamtam.ai/l/research-institutes-maryland) (52)
- [SaaS companies in Maryland](https://www.tamtam.ai/l/saas-companies-maryland) (52)
- [Companies with a mobile app in Maryland](https://www.tamtam.ai/l/companies-with-mobile-app-maryland) (49)
- [AI companies in Maryland](https://www.tamtam.ai/l/ai-companies-maryland) (48)

## 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)
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- [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)
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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 Michigan](https://www.tamtam.ai/l/professional-services-firms-michigan) (172)
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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-maryland