| Curio Systems GmbH | Bavaria |
| Curiosity GmbH | |
| Curious Capital | North Rhine-Westphalia |
| Curlee Design | |
| cursorsystems GmbH | Berlin |
| Cusp Capital Partners | North Rhine-Westphalia |
| Custify | |
| Customcells Itzehoe GmbH | |
| Customer Alliance GmbH | |
| CVC Revenue Solutions GmbH | |
| CVOsite GbR | Lower Saxony |
| CVS Ingenieurgesellschaft mbH | Bremen |
| CWA GmbH | Lower Saxony |
| CWK IT Consulting GmbH | Baden-Württemberg |
| CWS Computer & Webservices | Berlin |
| cxomni GmbH | |
| Cyanite.ai | |
| Cybay New Media GmbH | Lower Saxony |
| Cyber Output | |
| Cyber-Sicherheitsrat Deutschland e.V. | |
| Cyber.Core | Lower Saxony |
| Cyberday GmbH | Bavaria |
| CyberDesk GmbH | |
| Cyberlab GmbH | Berlin |
| Cyberpromote GmbH | Bavaria |
| cyberTECHNOLOGIES GmbH | |
| Cybervize | |
| cyberwebhosting.de | Hamburg |
| Cybox GmbH | Lower Saxony |
| Cybus GmbH | |
| Cycletech Multimedia GmbH | Hesse |
| Cyclic Design | |
| Cyclize GmbH | |
| Cyclotron ITK GmbH | Hesse |
| Cyclus Schulungszetrum | |
| Cycos AG | North Rhine-Westphalia |
| Cylib GmbH | |
| Cynfo GmbH | Lower Saxony |
| Cyntegrity Germany GmbH | |
| CyProtect AG | Bavaria |
| Cysal GmbH | |
| Cytena GmbH | |
| Cytion GmbH | |
| CYTOK GmbH | |
| Cytrus GmbH | Lower Saxony |
| CZEWO-DATA GmbH | Bavaria |
| d&b audiotechnik GmbH & Co. KG | |
| D&D Computer Service | |
| D&F ISP Ltd. & Co. KG | |
| D&G-Software GmbH | |