| CIC Consulting Informático | Cantabria |
| CIC nanoGUNE | |
| CIDETEC | |
| CIEM Zaragoza | |
| CIF, 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 |
| CITD Engineering & Technologies, S.L. | |
| 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 |
| Cloud District | Madrid |
| Cloud Incubator HUB | Murcia |
| Cloud Internet Operator, S.L. | Madrid |
| Cloud Studio | Madrid |
| Cloud Workspace Consulting, S.L. | Madrid |
| CloudAPPi, S.L. | Madrid |
| CloudFramework, S.L. | Madrid |
| CloudGuide | |
| Cloudi NextGen, S.L. | Barcelona |
| Cloudtango | Barcelona |
| Cloudworks | Barcelona |
| Cluster Saúde de Galicia | A Coruña |
| CMI Business School | |
| Cobee | Madrid |