# Professional services firms headquartered in Ontario
Tamtam tracks 211 professional services firms headquartered in Ontario. This list ranks the 50 largest by number of employees on LinkedIn, led by Colliers, Hatch and RBC Capital Markets. Their median headcount is 1,256. Half of them were founded in 1955 or later. The most common headquarters are Toronto (37), Mississauga (3) and Ottawa (3).
The professional services firms in Ontario listed here are predominantly large organizations, many with a global reach. Industries represented include real estate, financial services, engineering, and advertising. Companies like Colliers, Hatch, and RBC Capital Markets employ thousands, indicating a focus on comprehensive, large-scale operations. KPMG Canada provides audit, tax, and advisory services, while Other.β’ specializes in optimizing media spend for marketers.
A notable characteristic of these firms is their concentration in Toronto, which serves as a major hub for professional services. Most of the companies, such as PwC Canada and BMO Capital Markets, have their headquarters in the city. There is also a mix of long-established firms, like EXP founded in 1906, and more recent entrants such as LABORATORY, founded in 2016, reflecting both enduring presence and ongoing development in the sector.
π¨π¦ Ontario Β· 50 companies Β· Updated Nov 11, 2026
| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [Colliers](https://www.tamtam.ai/c/colliers) (colliers.com)
Offers real estate services, engineering solutions, and investment management, focusing on client success and delivering strong financial returns. | Real Estate | π¨π¦ Toronto | 29,561 | |
| 2 | [Hatch](https://www.tamtam.ai/c/hatch-mississauga) (hatch.com)
Global network of professionals dedicated to developing innovative solutions in metals, energy, infrastructure, digital, and investments sectors for lasting success and positive change worldwide | Professional Services | π¨π¦ Mississauga | 11,326 | 1955 |
| 3 | [RBC Capital Markets](https://www.tamtam.ai/c/rbc-capital-markets) (rbccm.com)
Global investment bank providing specialized expertise in capital markets, banking, and finance to corporations, institutional investors, asset managers, and governments across international markets. | Investment Banking | π¨π¦ Toronto | 11,098 | |
| 4 | [KPMG Canada](https://www.tamtam.ai/c/kpmg-canada) (kpmg.com)
Providing audit, tax, and advisory services to public, private, nonprofit, and public sector organizations across Canada with professionalism. | Financial Services | π¨π¦ Toronto | 10,017 | |
| 5 | [Other.β’](https://www.tamtam.ai/c/other-toronto) (weareother.ca)
Specialized paid media and performance creative agency helping marketers optimize media spend, achieve targets, and outperform competition with proven methodologies and successful campaigns | Advertising Services | π¨π¦ Toronto | 9,168 | 2015 |
| 6 | [PwC Canada](https://www.tamtam.ai/c/pwc-canada) (pwc.com)
Delivering audit assurance, risk management, tax, and consulting services to build trust and solve complex business problems through collective industry expertise. | Business Consulting and Services | π¨π¦ Toronto | 5,523 | |
| 7 | [BMO Capital Markets](https://www.tamtam.ai/c/bmo-capital-markets) (capitalmarkets.bmo.com)
A leading North American financial services provider offering a complete range of investment and corporate banking products to clients worldwide | Investment Banking | π¨π¦ Toronto | 5,451 | |
| 8 | [EXP](https://www.tamtam.ai/c/exp) (exp.com)
A global firm providing engineering, architecture, design, and consulting services, with a history dating back to 1906 and over 3,000 professionals delivering successful projects worldwide | Civil Engineering | π¨π¦ Brampton | 4,949 | 1906 |
| 9 | [Avison Young](https://www.tamtam.ai/c/avison-young) (avisonyoung.us)
Global real estate advisor creating value through collective intelligence, creativity, and agile thinking, with a focus on making a positive impact on people's lives | Real Estate | π¨π¦ Toronto | 3,517 | |
| 10 | [Livingston International](https://www.tamtam.ai/c/livingston-international) (livingstonintl.com)
Providing customs brokerage, trade consulting, global trade management, freight forwarding, and innovative automation technology solutions worldwide for businesses. | International Trade and Development | π¨π¦ Toronto | 2,735 | 1945 |
| 11 | [LABORATORY](https://www.tamtam.ai/c/laboratory) (wearelaboratory.com)
A full-service agency creating innovative marketing solutions without boundaries, collaborating closely with forward-thinking brands to deliver impactful strategies and designs | Advertising Services | π¨π¦ Toronto | 2,731 | 2016 |
| 12 | [Fasken](https://www.tamtam.ai/c/fasken) (fasken.com)
An international law firm with over 950 lawyers and offices on three continents, providing practical legal services for complex business and litigation challenges | Law Practice | π¨π¦ Toronto | 2,458 | |
| 13 | [Borden Ladner Gervais LLP (BLG)](https://www.tamtam.ai/c/borden-ladner-gervais-llp-blg) (blg.com)
A Canadian law firm offering bilingual services in common and civil law, with a national presence and global reach through an international network Contributing to communities through pro bono work and charitable initiatives | Law Practice | π¨π¦ Toronto | 2,290 | 1823 |
| 14 | [McCarthy TΓ©trault](https://www.tamtam.ai/c/mccarthy-tetrault) (mccarthy.ca)
Canadian-based law firm offering a wide range of legal services to Canadian and international clients, with expertise in business law, litigation, tax, real estate, and labor law | Law Practice | π¨π¦ Toronto | 2,088 | 1855 |
| 15 | [Klick](https://www.tamtam.ai/c/klick) (klick.com)
An independent commercialization partner for life sciences brands, focused on developing, launching, and supporting brands to maximize market potential globally | Advertising Services | π¨π¦ Toronto | 2,006 | 1997 |
| 16 | [Osler, Hoskin & Harcourt LLP](https://www.tamtam.ai/c/osler-hoskin-and-harcourt-llp) (osler.com)
providing business law advice and counsel to Canadian, U.S., and international clients on domestic and cross-border legal issues | Law Practice | π¨π¦ Toronto | 1,707 | 1862 |
| 17 | [Blake, Cassels & Graydon LLP](https://www.tamtam.ai/c/blake-cassels-and-graydon-llp) (blakes.com)
A top Canadian business law firm providing exceptional legal services to leading businesses in Canada and globally, with a focus on client relationships and expertise | Law Practice | π¨π¦ Toronto | 1,686 | 1856 |
| 18 | [Tundra Technical Solutions](https://www.tamtam.ai/c/tundra-technical-solutions) (tundratechnical.com)
Global provider of staffing solutions, focusing on understanding client and candidate needs to deliver top talent for the right role worldwide | Staffing and Recruiting | π¨π¦ Toronto | 1,679 | 2004 |
| 19 | [Gowling WLG Canada](https://www.tamtam.ai/c/gowling-wlg-canada) (gowlingwlg.com)
International legal organization formed through the merger of a Canadian and UK-based law firm, offering specialized legal services across 18 global locations | Law Practice | π¨π¦ Toronto | 1,572 | |
| 20 | [Stikeman Elliott LLP](https://www.tamtam.ai/c/stikeman-elliott-llp) (stikeman.com)
A global leader in Canadian business law, providing legal services and creative solutions in various practice areas to clients worldwide | Law Practice | π¨π¦ Toronto | 1,564 | 1952 |
| 21 | [Miller Thomson LLP](https://www.tamtam.ai/c/miller-thomson-llp) (millerthomson.com)
National business law firm with 525 lawyers in Canada offering litigation, mergers and acquisitions, corporate finance, tax, real estate, labor & employment services | Law Practice | π¨π¦ Toronto | 1,415 | 1957 |
| 22 | [Defence Construction Canada](https://www.tamtam.ai/c/defence-construction-canada) (dcc-cdc.gc.ca)
A Crown corporation providing contracting, construction management, infrastructure, environmental, and lifecycle support services for Canada's defence requirements through five service lines | Construction | π¨π¦ Ottawa | 1,372 | 1951 |
| 23 | [Kinectrics](https://www.tamtam.ai/c/kinectrics) (kinectrics.com)
Integrated lifecycle management services for electric power industry worldwide Testing, inspection, certification, engineering consulting, and maintenance services to ensure safe and efficient utility asset performance | Utilities | π¨π¦ Toronto | 1,361 | 1912 |
| 24 | [Procom](https://www.tamtam.ai/c/procom) (procomservices.com)
A leading staffing and contract workforce provider with 18 offices in North America, offering award-winning services to Fortune 500 clients | IT Services and IT Consulting | π¨π¦ Toronto | 1,287 | 1978 |
| 25 | [Dillon Consulting Limited](https://www.tamtam.ai/c/dillon-consulting-limited) (dillon.ca)
A Canadian employee-owned consulting firm specializing in planning, engineering, environmental science, and management, providing innovative solutions for complex projects | Business Consulting and Services | π¨π¦ Toronto | 1,256 | 1946 |
| 26 | [Kelly Services (Canada), Ltd.](https://www.tamtam.ai/c/kelly-services-canada-ltd) (kellyservices.ca)
This company is a global specialty talent solutions provider, connecting job seekers and employers in various fields, embracing nontraditional work arrangements | Staffing and Recruiting | π¨π¦ Mississauga | 1,247 | 1946 |
| 27 | [CONTAX Inc.](https://www.tamtam.ai/c/contax-inc) (contax.com)
Providing SAP system implementation, support, and maintenance services with a focus on quality, reliability, and customer business growth. | IT Services and IT Consulting | π¨π¦ Toronto | 1,227 | 1991 |
| 28 | [Randstad Canada](https://www.tamtam.ai/c/randstad-canada) (randstad.ca)
This company is a Canadian leader in recruitment and HR, focusing on delivering HR innovation with a people-first, human approach | Staffing and Recruiting | π¨π¦ Toronto | 1,203 | 1997 |
| 29 | [Drake International](https://www.tamtam.ai/c/drake-international) (drakeintl.com)
A global leader in flexible and permanent staffing, offering talent management solutions to maximize human capital assets and increase organizational bottom line | Human Resources Services | π¨π¦ Toronto | 1,189 | 1951 |
| 30 | [WSI World](https://www.tamtam.ai/c/wsi-world) (wsiworld.com)
Global leader in digital marketing, providing tailored solutions to unlock potential for brands across various industries with over 25 years of experience | Advertising Services | π¨π¦ Etobicoke | 1,174 | 1995 |
| 31 | [Torys LLP](https://www.tamtam.ai/c/torys-llp) (torys.com)
Providing superior counsel and client service, our cross-border team offers innovative solutions for clients' toughest problems with regional expertise | Law Practice | π¨π¦ Toronto | 1,106 | 1941 |
| 32 | [Bill Gosling Outsourcing India](https://www.tamtam.ai/c/bill-gosling-outsourcing-india) (billgosling.com)
Outsourcing solutions provider with 65+ years of experience in contact center industry, dedicated to helping brands reach their customers effectively and efficiently | Outsourcing and Offshoring Consulting | π¨π¦ Barrie | 1,101 | 2010 |
| 33 | [Baker Tilly Canada](https://www.tamtam.ai/c/baker-tilly-canada) (bakertilly.ca)
National association of chartered professional accounting firms providing audit, tax, and advisory solutions for diverse industries through an extensive independent member network. | Accounting | π¨π¦ Waterloo | 1,004 | |
| 34 | [Canaccord Genuity Group Inc.](https://www.tamtam.ai/c/canaccord-genuity-group-inc) (canaccordgenuity.com)
A leading independent financial services firm offering wealth management and capital markets services globally to individual, institutional, and corporate clients | Financial Services | π¨π¦ Toronto | 987 | 1950 |
| 35 | [Brock Solutions](https://www.tamtam.ai/c/brock-solutions) (brocksolutions.com)
Global industrial automation and professional services provider specializing in Manufacturing, Transportation, and Utilities with expertise in engineering software and solutions | Automation Machinery Manufacturing | π¨π¦ Kitchener | 976 | 1992 |
| 36 | [NORR](https://www.tamtam.ai/c/norr) (norr.com)
Employee-owned A&E firm with 800 professionals in various sectors across multiple countries, focusing on purpose-driven design for sustainable and inclusive spaces | Architecture and Planning | π¨π¦ Toronto | 947 | 1938 |
| 37 | [McMillan LLP](https://www.tamtam.ai/c/mcmillan-llp) (mcmillan.ca)
A national business law firm in Canada specializing in transportation, technology, infrastructure, natural resources, energy, cross-border transactions, private equity, real estate, and regulatory disputes | Law Practice | π¨π¦ Toronto | 935 | 1903 |
| 38 | [Cementation Americas](https://www.tamtam.ai/c/cementation-americas) (cementation.com)
Global mining services provider focused on underground mine contracting, engineering, and material handling solutions, committed to safety, value, and client satisfaction | Mining | π¨π¦ North Bay | 933 | 1998 |
| 39 | [RSM Canada](https://www.tamtam.ai/c/rsm-canada) (rsmcanada.com)
A leading global provider of assurance, tax, and consulting services with an integrated team of industry-focused experts across Canada and beyond | Accounting | π¨π¦ Toronto | 898 | |
| 40 | [Cassels Brock & Blackwell LLP](https://www.tamtam.ai/c/cassels-brock-and-blackwell-llp) (cassels.com)
A leading Canadian law practice specializing in business law, serving clients ranging from start-ups to multinational corporations with practical and flexible legal solutions | Law Practice | π¨π¦ Toronto | 874 | 1888 |
| 41 | [Pinchin in Canada](https://www.tamtam.ai/c/pinchin-in-canada) (pinchin.com)
An environmental consulting firm offering services in engineering, building science, health & safety, asbestos abatement, emissions reduction, and environmental compliance across North America | Environmental Services | π¨π¦ Mississauga | 871 | |
| 42 | [Marsh Canada](https://www.tamtam.ai/c/marsh-canada) (corporate.marsh.com)
Global leader in insurance brokering and risk advisory services, providing data-driven solutions to commercial and individual clients worldwide through multiple market-leading businesses | Insurance | π¨π¦ Toronto | 839 | 1914 |
| 43 | [Onex](https://www.tamtam.ai/c/onex) (onex.com)
Investor and asset manager with $496 billion assets under management, specializing in private equity and credit investments for global clients since 1984 | Investment Management | π¨π¦ Toronto | 808 | 1984 |
| 44 | [Davies Ward Phillips & Vineberg LLP](https://www.tamtam.ai/c/davies-ward-phillips-and-vineberg-llp) (dwpv.com)
A leading Canadian business law firm specializing in high-stakes matters, providing clarity, speed, and effective solutions for complex deals and cases Offices in Toronto, MontrΓ©al, and New York | Law Practice | π¨π¦ Toronto | 807 | |
| 45 | [Colliers Project Leaders \| Canada](https://www.tamtam.ai/c/colliers-project-leaders-canada) (colliersprojectleaders.com)
Project management partner offering total support for client success Dedicated project managers lead construction projects from start to finish, with career growth opportunities | Professional Services | π¨π¦ Ottawa | 747 | 1989 |
| 46 | [Grant Thornton LLP (Canada)](https://www.tamtam.ai/c/grant-thornton-llp-canada) (doanegrantthornton.ca)
A leading Canadian accounting and advisory firm, helping organizations unlock their potential with audit, advisory, and tax services Recognized for workplace excellence | Accounting | π¨π¦ Toronto | 725 | |
| 47 | [RWDI](https://www.tamtam.ai/c/rwdi) (rwdi.com)
The company specializes in innovative solutions for the built environment, focusing on building performance, climate engineering, and environmental engineering to create sustainable and resilient spaces | Civil Engineering | π¨π¦ Guelph | 723 | 1972 |
| 48 | [Cowater International](https://www.tamtam.ai/c/cowater-international) (cowater.com)
Global leader in management consulting focusing on developing and emerging economies Specializing in sustainable solutions for governments, organizations, and communities to create lasting impacts | International Trade and Development | π¨π¦ Ottawa | 712 | 1984 |
| 49 | [MCIS Language Solutions](https://www.tamtam.ai/c/mcis-language-solutions) (mcislanguages.com)
A not-for-profit social enterprise offering 24/7 solutions in over 350 languages, with a focus on financial sustainability, human rights, and diversity | Translation and Localization | π¨π¦ Toronto | 693 | 1989 |
| 50 | [CBRE Canada](https://www.tamtam.ai/c/cbre-canada) (cbre.ca)
Real estate firm offering comprehensive solutions globally, serving investors and tenants through a wide range of services including property management, investment management, and strategic consulting | Leasing Non-residential Real Estate | π¨π¦ Toronto | 679 | 1983 |
## 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 Ontario
- [The largest companies in Ontario](https://www.tamtam.ai/l/largest-companies-ontario) (5,032)
- [Multinational companies in Ontario](https://www.tamtam.ai/l/multinational-companies-ontario) (901)
- [Financial services firms in Ontario](https://www.tamtam.ai/l/financial-services-firms-ontario) (396)
- [Manufacturers in Ontario](https://www.tamtam.ai/l/manufacturers-ontario) (389)
- [Critical infrastructure operators in Ontario](https://www.tamtam.ai/l/critical-infrastructure-operators-ontario) (344)
- [Retail chains in Ontario](https://www.tamtam.ai/l/retail-chains-ontario) (327)
- [Companies with in-house R&D in Ontario](https://www.tamtam.ai/l/r-and-d-companies-ontario) (300)
- [Logistics companies in Ontario](https://www.tamtam.ai/l/logistics-companies-ontario) (285)
- [Education providers in Ontario](https://www.tamtam.ai/l/education-companies-ontario) (276)
- [SaaS companies in Ontario](https://www.tamtam.ai/l/saas-companies-ontario) (275)
- [Truck Transportation companies in Ontario](https://www.tamtam.ai/l/truck-transportation-companies-ontario) (270)
- [Transportation, Logistics, Supply Chain and Storage companies in Ontario](https://www.tamtam.ai/l/transportation-logistics-supply-chain-and-storage-companies-ontario) (261)
- [Public sector organisations in Ontario](https://www.tamtam.ai/l/public-sector-organisations-ontario) (259)
- [Financial Services companies in Ontario](https://www.tamtam.ai/l/financial-services-companies-ontario) (250)
- [IT Services and IT Consulting companies in Ontario](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-ontario) (235)
- [Software Development companies in Ontario](https://www.tamtam.ai/l/software-development-companies-ontario) (231)
- [Healthcare providers in Ontario](https://www.tamtam.ai/l/healthcare-providers-ontario) (226)
- [Hardware manufacturers in Ontario](https://www.tamtam.ai/l/hardware-companies-ontario) (213)
- [Hospitals and Health Care companies in Ontario](https://www.tamtam.ai/l/hospitals-and-health-care-companies-ontario) (205)
- [Distributors and wholesalers in Ontario](https://www.tamtam.ai/l/distributors-and-wholesalers-ontario) (183)
- [Companies with a mobile app in Ontario](https://www.tamtam.ai/l/companies-with-mobile-app-ontario) (181)
- [Publicly traded companies in Ontario](https://www.tamtam.ai/l/publicly-traded-companies-ontario) (156)
- [IT services companies in Ontario](https://www.tamtam.ai/l/it-services-companies-ontario) (156)
- [Subscription businesses in Ontario](https://www.tamtam.ai/l/subscription-businesses-ontario) (153)
## The same list elsewhere in Canada
- [Professional services firms in Canada](https://www.tamtam.ai/l/professional-services-firms-canada) (481)
- [Professional services firms in the province of Quebec](https://www.tamtam.ai/l/professional-services-firms-province-of-quebec) (103)
- [Professional services firms in Alberta](https://www.tamtam.ai/l/professional-services-firms-alberta) (81)
- [Professional services firms in British Columbia](https://www.tamtam.ai/l/professional-services-firms-british-columbia) (59)
- [Professional services firms in Toronto](https://www.tamtam.ai/l/professional-services-firms-toronto) (117)
- [Professional services firms in Montreal](https://www.tamtam.ai/l/professional-services-firms-montreal) (65)
- [Professional services firms in Calgary](https://www.tamtam.ai/l/professional-services-firms-calgary) (55)
- [Professional services firms in Vancouver](https://www.tamtam.ai/l/professional-services-firms-vancouver) (34)
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Source: https://www.tamtam.ai/l/professional-services-firms-ontario