| C. Gathmann Computer-System-Beratung GmbH | Bremen |
| C. Rudolf Salfer GmbH | Bavaria |
| C.A.I. Systeme GmbH | Berlin |
| C.A.T.S. Software GmbH | Hesse |
| C.A.T.S. Vertriebs GmbH | Bavaria |
| C.B.C. Computer Business Center GmbH | Hesse |
| C.I.C. Software GmbH | Bavaria |
| C1 DV Consulting GmbH | Bavaria |
| C3:net | Saarland |
| C4B Com for Business AG | Bavaria |
| C4C consulting GmbH | North Rhine-Westphalia |
| Cabacos CMS | Berlin |
| Cabanova GmbH | North Rhine-Westphalia |
| Cable Engineering-Nord GmbH | Mecklenburg-Vorpommern |
| CAD Dienstleistungen Stephan Knellesen | North Rhine-Westphalia |
| CAD Schroer GmbH | North Rhine-Westphalia |
| CAD'N ORG Engineering and Consulting GmbH | |
| CAD-Electronic Development Production GmbH | Bavaria |
| CAD-iS GmbH | Hesse |
| CAD-KAS Kassler Computersoftware GbR | Saxony |
| CAD-Service-München GmbH | Bavaria |
| CAD-Team | Hesse |
| CadCabel AG | Thuringia |
| Caddon Printing & Imaging GmbH | Baden-Württemberg |
| Cadeia GmbH | |
| Cadenzo.de | North Rhine-Westphalia |
| CADMAI | Bavaria |
| CAE Automation GmbH | Hesse |
| Caffeinated | |
| CAI Computerdesign | Hesse |
| Caigos GmbH | Saarland |
| Caipirinha Games GmbH | Schleswig-Holstein |
| Caisy | Baden-Württemberg |
| CAL Consult GmbH | Bavaria |
| Calenberger Kreditverein | |
| Call4Mac | Hamburg |
| Callas Software GmbH | Berlin |
| Calwa IT-Services GmbH | Hesse |
| Calyxo GmbH | Saxony-Anhalt |
| Cam Concept GmbH | Hesse |
| CAM Systems GmbH | Bavaria |
| Cam-Service GmbH | Lower Saxony |
| Camaix GmbH | North Rhine-Westphalia |
| CAMAO | Berlin |
| Cambrium GmbH | |
| CamData GmbH | North Rhine-Westphalia |
| Camelot ITLab GmbH | |
| CAMELOT Management Consultants AG | |
| Camido GmbH | Bavaria |
| Camino-Kommunikation GmbH | Hamburg |