| CannDoIT | Cork County Council |
| Canon Ireland | South Dublin County Council |
| Cantec | Waterford City and County Council |
| Captec | |
| Cara Partners | |
| CarbonSpace Ltd | |
| Cargo Defenders | |
| Carlow College, St. Patrick's | |
| Carr Communications Ltd | |
| CashAnalytics | |
| Cashbook Ltd | |
| Cashin Telecommunications Ltd | Dublin City Council |
| Catalyx | |
| Cavan Institute | |
| Caveo Information Systems Ltd | |
| CCSI Ltd | Dún Laoghaire-Rathdown County Council |
| CCT College Dublin | |
| CD Analytics | |
| CDG Brand | Dublin City Council |
| CeADAR | |
| Ceartas DMCA Ltd | |
| Cellusys | |
| Celtic Biotech Ltd | |
| Celtic Management Services | |
| Central Internet Cafe | Dublin City Council |
| Centre for Software Engineering | Dublin City Council |
| Centrestage | Dublin City Council |
| Centron System Solutions | |
| Cesanta | |
| Cetsoft | |
| Chanelle Pharma | |
| Channel Mechanics | |
| Channelship | |
| ChannelSight | |
| Chatspace AI | Galway City Council |
| CheckVentory Innovation Ltd | |
| Chillistore Technologies Ltd | |
| Chipright | Galway City Council |
| Chopcast | |
| Chuffey Design Company | Cork City Council |
| CI Studio | |
| Cicero Networks | |
| Circit Ltd | |
| City Colleges | |
| CitySwift | |
| CiviQ | |
| CJ Cube Technologies Ltd | |
| CK Website Design | |
| Clan Design Ltd | |
| Clanwilliam IRL | |