| CETMO | |
| Cetrex Internet Marketing, S.C.P. | Barcelona |
| CGB Informática | Salamanca |
| Challengers | Barcelona |
| Channel Partner | Madrid |
| char Desarrollo de Sistemas, S.L. | Barcelona |
| Chargy | Madrid |
| Charrua | A Coruña |
| Chekin | Sevilla |
| Chibig, S.L.U. | Valencia |
| ChronoScan Capture, S.L. | Madrid |
| CIAN, Servicios Informáticos, S.L. | Madrid |
| Cibersuite Networks, S.A. | Málaga |
| CIC biomaGUNE | |
| CIC Consulting Informático | Cantabria |
| CIC nanoGUNE | |
| CIDETEC | |
| CIEM Zaragoza | |
| CIF, S.L. | Madrid |
| CIMA Asesores EAF, S.L. | Madrid |
| Cima Horizons | Sevilla |
| Cima Informática | Alicante |
| CIMA Nuevas Tecnologías Informáticas, S.L. | Navarre |
| Cimaware Software | Madrid |
| Cimkey | Barcelona |
| Cimworks | Barcelona |
| Circular | Madrid |
| Círculo Web | Madrid |
| Cirrus GH Technology Company, S.L. | Madrid |
| CISET | Madrid |
| Citega, S.L. | Pontevedra |
| Citibeats | Barcelona |
| Citibox | Madrid |
| Citilab-Cornellà | Barcelona |
| Ciudadela Property Management, S.L. | |
| Classfile Education | Barcelona |
| Clave Informática, S.L. | Alicante |
| ClearPeaks | Barcelona |
| CLEVER Global | Sevilla |
| Cleverea, S.L. | Barcelona |
| Clevergy | Madrid |
| Clevisa | Madrid |
| Click Informática | Gipuzkoa |
| Clickedu | Barcelona |
| ClickInformatica | Balearic Islands |
| Clicks.Expert | Málaga |
| ClickSun | Balearic Islands |
| Clictoclic | Balearic Islands |
| Clínica Universidad de Navarra | |
| Cloespain Distribucion, S.L. | Cádiz |