# Top 30 professional services firms in Montreal

Tamtam tracks 65 professional services firms headquartered in Montreal. This list ranks the 30 largest by number of employees on LinkedIn, led by SNC-Lavalin, WSP in Canada and Logica. Their median headcount is 597. Half of them were founded in 1981 or later.

Montreal's professional services sector features a mix of large established firms and mid-sized companies, predominantly in engineering, IT consulting, and broader professional services. Notable firms include SNC-Lavalin, a global engineering and nuclear organization; WSP in Canada, which provides engineering, advisory, and science expertise; and Logica, a global provider of IT and business process services. Raymond Chabot Grant Thornton offers accounting and consulting, while Alithya specializes in digital technology services.

A clear pattern among these companies is their strong representation in engineering services, with firms like BPA, Artelia Canada, and gbi contributing to this cluster. Additionally, IT consulting and business consulting are well-represented, indicating a robust demand for specialized technical and strategic advice in the region. Most of these larger firms are headquartered in Montreal, serving both local and international clients.

🇨🇦 Montreal · 30 companies · Updated Nov 12, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [SNC-Lavalin](https://www.tamtam.ai/c/snc-lavalin) (atkinsrealis.com)<br>Global engineering services and nuclear organization connecting people, data, and technology to transform infrastructure and energy systems worldwide. | Civil Engineering | 🇨🇦 Montreal | 11,913 |  |
| 2 | [WSP in Canada](https://www.tamtam.ai/c/wsp-in-canada) (wsp.com)<br>professional services firm unites engineering, advisory, science expertise; shapes communities; advances humanity; delivers projects across sectors globally. | Professional Services | 🇨🇦 Montreal | 10,459 | 1959 |
| 3 | [Logica](https://www.tamtam.ai/c/logica) (cgi.com)<br>Global provider of IT and business process services, offering consulting, integration, and outsourcing with a team of 69,000 professionals across 40 countries | IT Services and IT Consulting | 🇨🇦 Montreal | 6,113 |  |
| 4 | [Raymond Chabot Grant Thornton](https://www.tamtam.ai/c/raymond-chabot-grant-thornton) (rcgt.com)<br>A leading accounting firm with over 2,300 professionals offering assurance, taxation, consulting, and business recovery services in Quebec and globally | Professional Services | 🇨🇦 Montreal | 2,426 | 1948 |
| 5 | [Alithya](https://www.tamtam.ai/c/alithya) (alithya.com)<br>A global digital technology services company providing practical IT solutions tailored to complex business challenges, with a focus on strategy and digital transformation | IT Services and IT Consulting | 🇨🇦 Montreal | 2,418 |  |
| 6 | [BPA](https://www.tamtam.ai/c/bpa-montreal) (bpa.ca)<br>An engineering firm specializing in mechanical, electrical, structural engineering, building science, and more for commercial, institutional, and industrial markets across Canada | Engineering Services | 🇨🇦 Montreal | 1,269 | 1956 |
| 7 | [COFOMO](https://www.tamtam.ai/c/cofomo) (cofomo.com)<br>Canadian IT and business consulting leader specializing in digital transformation with a team of 3,000 professionals offering innovative solutions nationwide | Business Consulting and Services | 🇨🇦 Montreal | 1,201 | 1995 |
| 8 | [AVENIR GLOBAL](https://www.tamtam.ai/c/avenir-global) (avenir.global)<br>A global holding and management group with specialized communication agencies in Canada, the US, Europe, and the Middle East | Public Relations and Communications Services | 🇨🇦 Montreal | 1,020 | 1976 |
| 9 | [Richter](https://www.tamtam.ai/c/richter) (richter.ca)<br>Business \| Family Office providing strategic advice on business and family matters, guiding successful entrepreneurs to shape their legacy across generations | Professional Services | 🇨🇦 Montreal | 922 | 1926 |
| 10 | [Stantec au Québec](https://www.tamtam.ai/c/stantec-au-quebec) (stantec.com)<br>Global leader in engineering and sustainable development, with expertise in various sectors, providing services from concept to completion with innovation and client needs in mind | Business Consulting and Services | 🇨🇦 Montreal | 801 | 1954 |
| 11 | [BCF](https://www.tamtam.ai/c/bcf) (bcf.ca)<br>Leading team of over 500 professionals providing innovative solutions for businesses in Quebec and beyond, recognized as Canada's Best Managed for 12 years | Law Practice | 🇨🇦 Montreal | 761 | 1995 |
| 12 | [SNC-Lavalin Rail & Transit (formerly Interfleet)](https://www.tamtam.ai/c/snc-lavalin-rail-and-transit-formerly-interfleet) (snclavalin.com)<br>Global engineering and construction group providing industry-leading services in infrastructure, oil and gas, mining, power, and rail and transit systems | Truck Transportation | 🇨🇦 Montreal | 659 | 1911 |
| 13 | [Artelia Canada](https://www.tamtam.ai/c/artelia-canada) (arteliagroup.ca)<br>Multidisciplinary engineering firm providing innovative solutions in mobility, energy, environment, water, industry, and telecom across Canada with global expertise. | Engineering Services | 🇨🇦 Montreal | 642 |  |
| 14 | [gbi](https://www.tamtam.ai/c/gbi) (gbi.ca)<br>With over 60 years of experience, we specialize in innovative and sustainable engineering solutions for various sectors, including residential, education, healthcare, and infrastructure | Engineering Services | 🇨🇦 Montreal | 614 | 1963 |
| 15 | [Lavery](https://www.tamtam.ai/c/lavery) (lavery.ca)<br>Leading independent law firm providing personalized and innovative legal solutions to domestic and international organizations in Quebec with a team of 250 professionals | Law Practice | 🇨🇦 Montreal | 597 | 1913 |
| 16 | [LAPORTE](https://www.tamtam.ai/c/laporte) (laporteconsultants.com)<br>Specialized engineering firm providing process, building, and utility design solutions to Pharmaceutical, Agrifood, and Bioindustrial industries globally with long-term client relationships | Engineering Services | 🇨🇦 Montreal | 543 | 1999 |
| 17 | [Groupe ABS](https://www.tamtam.ai/c/groupe-abs) (groupeabs.com)<br>Established in 1993, Groupe ABS offers a wide range of services in material engineering, geotechnics, environmental science, and specialized divisions in drilling and contaminated soil treatment | Civil Engineering | 🇨🇦 Montreal | 492 | 1993 |
| 18 | [FBL S.E.N.C.R.L. Société de comptables professionnels agréés](https://www.tamtam.ai/c/fbl-s-e-n-c-r-l-societe-de-comptables-professionnels-agrees) (fbl.com)<br>A top accounting firm in Quebec with over 40 years of experience offering services in accounting, taxation, business valuation, financing, and international assistance | Accounting | 🇨🇦 Montreal | 488 | 1981 |
| 19 | [Tetra Tech au Québec](https://www.tamtam.ai/c/tetra-tech-au-quebec) (tetratech.com)<br>A global leader in consulting, engineering, and technical services with expertise in various sectors, providing innovative solutions for projects worldwide | Civil Engineering | 🇨🇦 Montreal | 485 |  |
| 20 | [Indero (formerly Innovaderm)](https://www.tamtam.ai/c/indero-formerly-innovaderm) (inderocro.com)<br>A specialized CRO in dermatology, providing expert guidance and services for Phase 1 to Phase IV studies worldwide since 2000 | Research Services | 🇨🇦 Montreal | 480 | 2000 |
| 21 | [AAA Canada](https://www.tamtam.ai/c/aaa-canada) (aaa-canada.ca)<br>Providing subcontracting, technical assistance, and productivity solutions in Aerospace, Ground Transportation, and Defense sectors worldwide through international expertise | Outsourcing and Offshoring Consulting | 🇨🇦 Montreal | 440 | 2008 |
| 22 | [GCM Consultants](https://www.tamtam.ai/c/gcm-consultants) (gcmconsultants.com)<br>The company delivers high-performance engineering services for various industrial sectors, offering studies, engineering, project management, and construction services for projects up to $200M | Business Consulting and Services | 🇨🇦 Montreal | 432 |  |
| 23 | [Leger](https://www.tamtam.ai/c/leger) (leger360.com)<br>A leading Canadian market research and analytics company with over 600 employees across 8 offices, serving prestigious clients since 1986 | Market Research | 🇨🇦 Montreal | 428 | 1986 |
| 24 | [Beyond Technologies](https://www.tamtam.ai/c/beyond-technologies) (beyondtechnologies.com)<br>Professional services specializing in SAP integration and business process optimization, leveraging extensive industry expertise to deliver practical, innovative solutions. | IT Services and IT Consulting | 🇨🇦 Montreal | 414 | 2005 |
| 25 | [Lemay](https://www.tamtam.ai/c/lemay) (lemay.com)<br>Architects and designers focused on sustainable development, creating innovative spaces for growth, and recognized for management excellence and environmental commitment | Architecture and Planning | 🇨🇦 Montreal | 403 | 1957 |
| 26 | [Normandin Beaudry](https://www.tamtam.ai/c/normandin-beaudry) (normandin-beaudry.ca)<br>Established in 1992, this consulting firm in Montreal, Toronto, and Quebec City specializes in human capital and financial performance through advisory services in eight areas of expertise | Human Resources Services | 🇨🇦 Montreal | 401 | 1992 |
| 27 | [Sid Lee](https://www.tamtam.ai/c/sid-lee) (sidlee.com)<br>Multidisciplinary creative community specializing in brand building, expression, and experience through design, advertising, architecture, and interactive communication. | Advertising Services | 🇨🇦 Montreal | 398 | 1993 |
| 28 | [Mecanica](https://www.tamtam.ai/c/mecanica) (mecanicasolutions.com)<br>Global provider of engineering services for aerospace, automotive, and AEC industries Specializing in PLM/CAD/CAM solutions, onsite support, R&D, engineering services, and custom software development for clients | Engineering Services | 🇨🇦 Montreal | 393 | 1983 |
| 29 | [Langlois Avocats](https://www.tamtam.ai/c/langlois-avocats) (langlois.ca)<br>Leading independent law firm in Quebec with over 175 lawyers offering high-quality legal services in various areas such as construction, energy, life sciences, and more | Law Practice | 🇨🇦 Montreal | 382 | 1916 |
| 30 | [Quantum Management Services Ltd.](https://www.tamtam.ai/c/quantum-management-services-ltd) (quantum.ca)<br>A recruitment agency with 55 years of experience, connecting organizations and individuals for permanent, contract, and temporary positions across various industries | Staffing and Recruiting | 🇨🇦 Montreal | 362 | 1968 |

## 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 12, 2026.

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- [Professional services firms in Ontario](https://www.tamtam.ai/l/professional-services-firms-ontario) (211)
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- [Professional services firms in Vancouver](https://www.tamtam.ai/l/professional-services-firms-vancouver) (34)

## The same list elsewhere

- [Professional services firms in the world](https://www.tamtam.ai/l/professional-services-firms-in-the-world) (24,737)

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