# Professional services firms headquartered in Connecticut

Tamtam tracks 54 professional services firms headquartered in Connecticut. This list ranks the 50 largest by number of employees on LinkedIn, led by TRC Companies, Inc., Daymon and ISG (Information Services Group). Their median headcount is 369. Half of them were founded in 1996 or later. The most common headquarters are Stamford (8), New Haven (6) and Hartford (5).

These professional services firms in Connecticut are mainly in business and IT consulting, engineering, and legal services. They include both large, established companies and firms founded in the 2000s. TRC Companies, Inc. provides advisory and engineering services, Daymon offers private brand development, ISG (Information Services Group) is an AI-focused technology research firm, and Robinson+Cole is a law firm.

Most of these companies are headquartered in Stamford and Hartford, indicating a concentration of professional services in these two cities. The list also shows a blend of industries, from environmental services and civil engineering to specialized IT solutions and financial consulting.

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

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [TRC Companies, Inc.](https://www.tamtam.ai/c/trc-companies-inc) (trccompanies.com)<br>Providing advisory, consulting, construction, engineering, and management services to help clients adapt and achieve sustainable, impactful results. | Environmental Services | 🇺🇸 Windsor | 7,463 | 1969 |
| 2 | [Daymon](https://www.tamtam.ai/c/daymon) (daymon.com)<br>Provides end-to-end private brand development services including strategy, product development, quality assurance, supplier management, sales, and branding solutions. | Business Consulting and Services | 🇺🇸 Stamford | 2,262 | 1970 |
| 3 | [ISG (Information Services Group)](https://www.tamtam.ai/c/isg-information-services-group) (isg-one.com)<br>Global AI-focused technology research and advisory firm helping organizations optimize technology investments and achieve operational excellence and growth. | Information Services | 🇺🇸 Stamford | 2,189 | 2006 |
| 4 | [Rizing](https://www.tamtam.ai/c/rizing) (rizing.com)<br>A global SAP partner offering strategy, implementation, and support for SAP HCM, EAM, and Retail/Fashion industries, driving business transformation with industry expertise | IT Services and IT Consulting | 🇺🇸 Stamford | 989 | 2006 |
| 5 | [SDG Corporation](https://www.tamtam.ai/c/sdg-corporation) (sdgc.com)<br>A global provider of technology and consulting services specializing in cybersecurity, identity, and risk management solutions for enterprises worldwide | IT Services and IT Consulting | 🇺🇸 Norwalk | 754 | 1993 |
| 6 | [Robinson+Cole](https://www.tamtam.ai/c/robinson-cole) (rc.com)<br>A law firm offering a range of legal services to regional, national, and international clients, with a focus on community involvement and client service excellence | Law Practice | 🇺🇸 Hartford | 681 | 1845 |
| 7 | [VLink Inc](https://www.tamtam.ai/c/vlink-inc) (vlinkinfo.com)<br>Global software engineering partner providing AI-powered solutions, custom product engineering, cloud modernization, and technical talent through onshore and offshore delivery models for enterprises. | Software Development | 🇺🇸 South Windsor | 623 | 2006 |
| 8 | [The Entrepreneur's Source](https://www.tamtam.ai/c/the-entrepreneur-s-source) (entrepreneurssource.com)<br>This company helps individuals achieve their Income, Lifestyle, Wealth, and Equity goals through Career Ownership with coaching, resources, and a unique Discovery Experience | Professional Training and Coaching | 🇺🇸 Southbury | 603 | 1984 |
| 9 | [SimiTree](https://www.tamtam.ai/c/simitree) (simitreehc.com)<br>SimiTree provides a wide range of support services and consulting to post-acute organizations in the healthcare industry to improve performance and revenue | Hospitals and Health Care | 🇺🇸 Hamden | 526 | 2011 |
| 10 | [Butler Aerospace & Defense](https://www.tamtam.ai/c/butler-aerospace-and-defense) (butler.com)<br>Specializing in state-of-the-art, cost-optimized solutions, we cater to Aerospace, Defense, and Federal markets by offering high-end engineering talent and flexible business models | Engineering Services | 🇺🇸 Shelton | 521 | 1947 |
| 11 | [Interpreters and Translators, Inc](https://www.tamtam.ai/c/interpreters-and-translators-inc) (ititranslates.com)<br>A language agency providing translation, interpreting, and training services Specializing in medical interpretation, language assessments, localization, and document translations | Translation and Localization | 🇺🇸 Glastonbury | 514 | 1986 |
| 12 | [Rizing Consumer Industries](https://www.tamtam.ai/c/rizing-consumer-industries) (rizing.com)<br>Leader in retail and consumer products for SAP software, providing specialized solutions and consulting services to optimize SAP experience worldwide | IT Services and IT Consulting | 🇺🇸 Stamford | 505 |  |
| 13 | [BL Companies](https://www.tamtam.ai/c/bl-companies) (blcompanies.com)<br>Company offering integrated architecture, engineering, environmental sciences, land surveying, and planning services with a focus on quality, employee ownership, and work-life balance | Civil Engineering | 🇺🇸 Meriden | 498 | 1986 |
| 14 | [USI Consulting Group](https://www.tamtam.ai/c/usi-consulting-group) (usicg.com)<br>A leading retirement plan consulting and benefits administration firm, providing comprehensive guidance and innovative solutions for employers and their employees nationwide | Financial Services | 🇺🇸 Glastonbury | 494 |  |
| 15 | [Fuss & O'Neill](https://www.tamtam.ai/c/fuss-and-o-neill) (fando.com)<br>A full-service engineering and planning firm with over 95 years of experience, serving public and private sectors across the East Coast | Civil Engineering | 🇺🇸 Hartford | 484 | 1924 |
| 16 | [GOA](https://www.tamtam.ai/c/goa) (goaarchitecture.com)<br>We are an architecture firm that integrates design and building production with a focus on sustainability, innovative technologies, and community-centric spaces | Architecture and Planning | 🇺🇸 New Haven | 450 | 1998 |
| 17 | [iTech Solutions](https://www.tamtam.ai/c/itech-solutions) (itechsolutions.com)<br>National IT staffing and recruiting firm with strong relationships with consultants and clients Specializes in contract, contract-to-hire, and direct hire positions for IT professionals | IT Services and IT Consulting | 🇺🇸 Farmington | 448 | 1995 |
| 18 | [Panzer Solutions LLC](https://www.tamtam.ai/c/panzer-solutions-llc) (panzersolutions.com)<br>Specializing in technology and consulting services, this company delivers innovation, quality, and value for clients, bridging the gap between technology and clients' needs | Staffing and Recruiting | 🇺🇸 Norwalk | 436 | 2010 |
| 19 | [Global Medical Virtual Assistants (GMVA)](https://www.tamtam.ai/c/global-medical-virtual-assistants-gmva) (globalmedicalva.com)<br>Providing top-tier Medical Virtual Assistant services to healthcare industry clients, assisting with digital administrative tasks like referrals, data verification, and patient follow-up | Hospitals and Health Care | 🇺🇸 West Hartford | 431 | 2019 |
| 20 | [LogicSource, Inc.](https://www.tamtam.ai/c/logicsource-inc) (logicsource.com)<br>LogicSource specializes in procurement services for indirect goods, helping brands optimize spending through expertise, technology, and strategic partnerships. | Business Consulting and Services | 🇺🇸 Westport | 423 | 2009 |
| 21 | [Sonalysts, Inc.](https://www.tamtam.ai/c/sonalysts-inc) (sonalysts.com)<br>An employee-owned small business providing integrated advanced technology solutions, video production, sound stages, animation, VFX, and a world-class recording studio | Defense and Space Manufacturing | 🇺🇸 Waterford | 413 | 1973 |
| 22 | [AI Engineers, Inc.](https://www.tamtam.ai/c/ai-engineers-inc) (aiengineers.com)<br>A multidisciplinary engineering firm providing innovative solutions for infrastructure needs, prioritizing accountability, entrepreneurship, innovation, inclusiveness, and transparency to benefit communities | Civil Engineering | 🇺🇸 Middletown | 411 | 1991 |
| 23 | [Lockwood](https://www.tamtam.ai/c/lockwood) (thelockwoodgrp.com)<br>The company collaborates with pharmaceutical, biotech, and medical device industries to create evidence-based, impactful strategies and communications for brand development | Advertising Services | 🇺🇸 Stamford | 405 | 2007 |
| 24 | [Zaelab](https://www.tamtam.ai/c/zaelab) (zaelab.com)<br>Highly-skilled digital partner advising global B2B organizations on delivering next-generation digital solutions to market | Business Consulting and Services | 🇺🇸 Westport | 391 | 2010 |
| 25 | [Wiggin and Dana LLP](https://www.tamtam.ai/c/wiggin-and-dana-llp) (wiggin.com)<br>A full-service law firm with offices across the United States, providing high-quality legal services for clients on complex matters | Law Practice | 🇺🇸 New Haven | 369 | 1934 |
| 26 | [Shipman & Goodwin LLP](https://www.tamtam.ai/c/shipman-and-goodwin-llp) (shipmangoodwin.com)<br>A trusted advisor providing tailored legal solutions to help clients achieve their goals in various industries and navigate complex transactions | Law Practice | 🇺🇸 Hartford | 362 | 1919 |
| 27 | [InGenius Prep](https://www.tamtam.ai/c/ingenius-prep) (ingeniusprep.com)<br>Expert team of former admissions officers and top graduate coaches providing admissions tips and guidance for success in the admissions process | E-Learning Providers | 🇺🇸 New Haven | 343 | 2012 |
| 28 | [Onward Search](https://www.tamtam.ai/c/onward-search) (onwardsearch.com)<br>Provides expert talent and innovative solutions for creative, marketing, and technology teams to achieve digital accessibility and AI transformation. | Staffing and Recruiting | 🇺🇸 Norwalk | 326 | 2007 |
| 29 | [GIT-Global Intelligence Technology](https://www.tamtam.ai/c/git-global-intelligence-technology) (git-link.com)<br>An IT services company offering cost-effective solutions with a focus on cultural affinity, collaborative business perspective, and skilled professionals in various industries | IT Services and IT Consulting | 🇺🇸 Hamden | 315 | 2003 |
| 30 | [Comply Regulatory Services](https://www.tamtam.ai/c/comply-regulatory-services) (comply.com)<br>An advanced provider of compliance and registration products and services for financial institutions, offering expert consulting and education to navigate regulatory requirements | Financial Services | 🇺🇸 Lakeville | 312 | 1984 |
| 31 | [Consulting Engineering Services (CES)](https://www.tamtam.ai/c/consulting-engineering-services-ces) (ceseng.com)<br>Specializes in sustainable MEP/FP engineering for commercial and residential buildings, focusing on energy efficiency, net-zero, and resilient design. | Engineering Services | 🇺🇸 Middletown | 306 | 1994 |
| 32 | [GSS](https://www.tamtam.ai/c/gss-bethel) (searchgss.com)<br>Global recruitment firm specializing in senior executives and medical/scientific leaders for biopharmaceutical/life science companies Experienced, consultative approach with milestone-based fee structure | Staffing and Recruiting | 🇺🇸 Bethel | 248 | 2005 |
| 33 | [MTU Aero Engines North America](https://www.tamtam.ai/c/mtu-aero-engines-north-america) (mtuusa.com)<br>Specializing in complete engineering services for the gas turbine industry, providing design, analysis, project management, and aftermarket engineering solutions tailored to individual needs | Aviation and Aerospace Component Manufacturing | 🇺🇸 Rocky Hill | 220 | 2000 |
| 34 | [Creative Concepts](https://www.tamtam.ai/c/creative-concepts) (creative-conceptsllc.com)<br>A pioneering consultancy specializing in digital, marketing, and communications services for national and international clients, with a focus on innovation and collaboration | Marketing Services | 🇺🇸 Fairfield | 206 | 2003 |
| 35 | [Maganti IT Resources, LLC](https://www.tamtam.ai/c/maganti-it-resources-llc) (mitresource.com)<br>A leading IT Software development and consulting firm, specializing in designing and delivering technology solutions to help clients gain a competitive edge | IT Services and IT Consulting | 🇺🇸 Waterbury | 198 | 2004 |
| 36 | [Daversa](https://www.tamtam.ai/c/daversa) (daversa.com)<br>Executive search firm specializing in building leadership teams for growth-stage, venture-backed technology companies with global market insight. | Staffing and Recruiting | 🇺🇸 Westport | 196 | 1993 |
| 37 | [Visionary Innovative Technology Solutions LLC](https://www.tamtam.ai/c/visionary-innovative-technology-solutions-llc) (vitsus.com)<br>A staffing and consulting firm partnering with clients globally to improve work efficiency and foster relationships across various industries | IT Services and IT Consulting | 🇺🇸 Plantsville | 99 | 2017 |
| 38 | [Titan Energy](https://www.tamtam.ai/c/titan-energy) (titanenergyne.com)<br>A leading energy consultant providing procurement, on-site generation, and tailored solutions to nonprofit, commercial, and industrial clients across the US | Utilities | 🇺🇸 Hartford | 68 | 2001 |
| 39 | [Zinoit LLC](https://www.tamtam.ai/c/zinoit-llc) (zinoit.com)<br>B2B lead generation & appointment setting company utilizing technology for demand generation, data mining, and marketing services with a focus on ROI and industry-specific expertise | Marketing Services | 🇺🇸 New Haven | 56 | 2017 |
| 40 | [Portfolio Advisors](https://www.tamtam.ai/c/portfolio-advisors) (portad.com)<br>Global private asset manager specializing in US middle market, offering tailored private equity, credit, and real estate investment solutions through customized programs worldwide | Financial Services | 🇺🇸 Darien | 54 | 1994 |
| 41 | [The Millard Group](https://www.tamtam.ai/c/the-millard-group) (themillardgroup.com)<br>Specializing in technology search, this firm delivers top talent using a scientific approach, sector expertise, and long-term partnerships for client success globally | Staffing and Recruiting | 🇺🇸 Middletown | 37 | 1996 |
| 42 | [Bank Street Group](https://www.tamtam.ai/c/bank-street-group) (bankstreet.com)<br>Independent investment banking firm offering financial advisory, M&A, private placements, restructuring, valuations, and fairness opinions to middle-market companies with experienced senior professionals | Investment Banking | 🇺🇸 Stamford | 32 | 2002 |
| 43 | [Apple Consulting Group Inc](https://www.tamtam.ai/c/apple-consulting-group-inc) (appleconsultinggroup.com)<br>Innovative consulting firm specializing in new technology, cloud solutions, digital transformation, and business systems improvement across various sectors | IT Services and IT Consulting | 🇺🇸 Trumbull | 22 | 2010 |
| 44 | [Martin LLP](https://www.tamtam.ai/c/martin-llp) (martinllp.net)<br>A sophisticated law practice with attorneys specializing in corporate, litigation, and real estate matters, providing personalized and proactive legal advice to clients | Law Practice | 🇺🇸 Stamford | 21 | 1996 |
| 45 | [Bershtein, Volpe & McKeon, PC](https://www.tamtam.ai/c/bershtein-volpe-and-mckeon-pc) (bvmlaw.com)<br>Specializing in various legal areas including health care, real estate, finance, litigation, bankruptcy, cannabis, non-profit governance, and estate administration | Law Practice | 🇺🇸 New Haven | 13 | 1996 |
| 46 | [Crumbie Law Group, LLC](https://www.tamtam.ai/c/crumbie-law-group-llc) (http)<br>A corporate and business law firm serving sophisticated municipal and Fortune 100/500 clients, specializing in MBE certification in New England | Legal Services | 🇺🇸 Hartford | 12 | 2008 |
| 47 | [Brooks, Houghton & Company, Inc.](https://www.tamtam.ai/c/brooks-houghton-and-company-inc) (brookshoughton.com)<br>A merchant banking firm providing investment banking services, direct investments, debt/equity placements, M&A advisory, valuation opinions, and corporate finance solutions globally | Investment Banking | 🇺🇸 Stamford | 12 | 1989 |
| 48 | [Maya Murphy, P.C.](https://www.tamtam.ai/c/maya-murphy-p-c) (mayalaw.com)<br>A law firm with attorneys practicing in various areas of law, offering personalized representation and serving clients in multiple states | Law Practice | 🇺🇸 Westport | 11 | 1994 |
| 49 | [Conway, Londregan, Sheehan & Monaco, P.C.](https://www.tamtam.ai/c/conway-londregan-sheehan-and-monaco-p-c) (conwaylondregan.com)<br>A multidisciplinary law firm providing legal services in litigation, real estate, municipal, labor and employment, and trust and estate matters | Legal Services | 🇺🇸 New London | 11 | 1962 |
| 50 | [Winchester Capital](https://www.tamtam.ai/c/winchester-capital) (winchestercapital.com)<br>Privately-owned investment banking firm offering strategic advisory services, international asset management, and expertise in cross-border mergers & acquisitions for global clients | Investment Banking | 🇺🇸 New Haven | 11 | 1986 |

## 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 Connecticut

- [The largest companies in Connecticut](https://www.tamtam.ai/l/largest-companies-connecticut) (1,247)
- [Multinational companies in Connecticut](https://www.tamtam.ai/l/multinational-companies-connecticut) (220)
- [Financial services firms in Connecticut](https://www.tamtam.ai/l/financial-services-firms-connecticut) (172)
- [Manufacturers in Connecticut](https://www.tamtam.ai/l/manufacturers-connecticut) (143)
- [Companies with in-house R&D in Connecticut](https://www.tamtam.ai/l/r-and-d-companies-connecticut) (101)
- [Education providers in Connecticut](https://www.tamtam.ai/l/education-companies-connecticut) (92)
- [Financial Services companies in Connecticut](https://www.tamtam.ai/l/financial-services-companies-connecticut) (92)
- [Hardware manufacturers in Connecticut](https://www.tamtam.ai/l/hardware-companies-connecticut) (86)
- [Critical infrastructure operators in Connecticut](https://www.tamtam.ai/l/critical-infrastructure-operators-connecticut) (85)
- [Healthcare providers in Connecticut](https://www.tamtam.ai/l/healthcare-providers-connecticut) (79)
- [Hospitals and Health Care companies in Connecticut](https://www.tamtam.ai/l/hospitals-and-health-care-companies-connecticut) (76)
- [Retail chains in Connecticut](https://www.tamtam.ai/l/retail-chains-connecticut) (72)
- [Investment Management companies in Connecticut](https://www.tamtam.ai/l/investment-management-companies-connecticut) (72)
- [Venture capital and private equity firms in Connecticut](https://www.tamtam.ai/l/vc-and-private-equity-firms-connecticut) (66)
- [Aerospace and defence companies in Connecticut](https://www.tamtam.ai/l/aerospace-and-defense-companies-connecticut) (58)
- [IT Services and IT Consulting companies in Connecticut](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-connecticut) (57)
- [IT services companies in Connecticut](https://www.tamtam.ai/l/it-services-companies-connecticut) (51)
- [Publicly traded companies in Connecticut](https://www.tamtam.ai/l/publicly-traded-companies-connecticut) (49)
- [Insurance companies in Connecticut](https://www.tamtam.ai/l/insurance-companies-connecticut) (45)
- [Contract manufacturers in Connecticut](https://www.tamtam.ai/l/contract-manufacturers-connecticut) (44)
- [SaaS companies in Connecticut](https://www.tamtam.ai/l/saas-companies-connecticut) (44)
- [Companies with a mobile app in Connecticut](https://www.tamtam.ai/l/companies-with-mobile-app-connecticut) (43)
- [Higher Education companies in Connecticut](https://www.tamtam.ai/l/higher-education-companies-connecticut) (43)
- [Public sector organisations in Connecticut](https://www.tamtam.ai/l/public-sector-organisations-connecticut) (42)

## 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)

---

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