| OSI Maritime Systems | British Columbia |
| OSI Network Solutions, Inc. | Alberta |
| Osidosi | Alberta |
| OSINT Techniques | |
| Ositech Communications, Inc. | Ontario |
| OSM | Ontario |
| Osmos Cloud | |
| Osnium Software, Inc. | Ontario |
| OSO Creative | Alberta |
| Osprey Marketing | New Brunswick |
| Ostia Sciences, Inc. | |
| Ostrog Computers | Ontario |
| OTEC Solutions | Ontario |
| OTM Orditechnicienmobile | Quebec |
| Otorobots Canada, Inc. | |
| OTR Web Solutions | Alberta |
| Otrofy, Inc. | |
| OTS | |
| OTT Group | |
| Ottawa Board of Trade | Ontario |
| Ottawa Business Journal | |
| Ottawa Computech | Ontario |
| Ottawa IT Consulting, Inc. | |
| Ottawa Logo Design | Ontario |
| Ottawa Marketing Guys | |
| Ottawa PC Users’ Group | Ontario |
| Ottawa Perl Mongers | Ontario |
| Ottawa Python Authors Group | Ontario |
| Ottawa Robotics Enthusiasts | Ontario |
| Ottawa SEO, Inc. | |
| Ottawa Tech Heroes | Ontario |
| Ottawa Web Design | |
| Ottawa's Best Tech Support | |
| Ottawa-Canada BSD Users Group | Ontario |
| OttawaComputerServices | Ontario |
| Otto Capital | |
| Oulton College | New Brunswick |
| Our Little Domains | British Columbia |
| Our Media Canada | |
| ourCIO Ltd | Manitoba |
| Out-Smarts | British Columbia |
| Out-There | Ontario |
| Outbox Technology, Inc. | Quebec |
| Outbrave Digital Ltd | |
| Outcome Marketing | British Columbia |
| Outcome3 | British Columbia |
| Outcrop Communications | Yukon |
| Outer-Net Technology, Inc. | Ontario |
| Outlaw Automation, Inc. | Alberta |
| Outrageous Creations | Ontario |