| ATEQ Canada, Inc. | Ontario |
| Aterlo Networks | Ontario |
| Athabasca University | Alberta |
| Athabasca University - Faculty of Science and Technology | Alberta |
| Athabsca University - Major in Computing and Information Systems | Alberta |
| Athena Computer Solutions | Nova Scotia |
| Athena Software | Ontario |
| ATHENA Technolo-G, Inc. | Quebec |
| Athennian | |
| AthleteMonitoring.com | |
| ATI Cables | Ontario |
| ATIC Computers | British Columbia |
| Atiigo Media | Nunavut |
| Atimi Software, Inc. | British Columbia |
| Atlantic 1801 | |
| Atlantic Association of Community Business Development Corporations | |
| Atlantic BIOCON | |
| Atlantic BioCorp | |
| Atlantic Canada Aerospace and Defence Association | |
| Atlantic Canada Opportunities Agency | New Brunswick |
| Atlantic Cell Phone Repair | |
| Atlantic Chamber of Commerce | |
| Atlantic Computational Excellence Network | New Brunswick |
| Atlantic Electronics Ltd | Nova Scotia |
| Atlantic FinTech | Nova Scotia |
| Atlantic Institute for Resilience, Inc. | |
| Atlantic Technology Centre | |
| Atlantic Technology Summit | Nova Scotia |
| Atlantic Venture Forum | Nova Scotia |
| Atlantic Webfitters | Nova Scotia |
| atlantiq AI Automation Solutions Ltd | |
| Atlas Agency, Inc. | Ontario |
| Atlas Communications | |
| Atlas Micronet, Inc. | Ontario |
| AtlasTrax Communication Corporation | Ontario |
| Atleon, Inc. | Quebec |
| ATM Consulting | Ontario |
| ATM Web Design, Inc. | Ontario |
| Atmacinta | Quebec |
| ATNM Digital Solutions Ltd | |
| Atoll Digital | |
| Atomic 55 Internet Technologies, Inc. | |
| Atomic Crayon | British Columbia |
| Atomic Energy of Canada Ltd | |
| Atomic IT | |
| Atomic Motion | Ontario |
| Atomic X | |
| AtomicX | Ontario |
| Atominos Consulting | |
| Atomlabs Digital Marketing | Ontario |