| Cybus GmbH | |
| Cycle | |
| Cycletech Multimedia GmbH | Hesse |
| Cyclic Design | |
| Cyclotron ITK GmbH | Hesse |
| Cyclus Schulungszetrum | |
| Cycos AG | North Rhine-Westphalia |
| Cylib GmbH | |
| Cynfo GmbH | Lower Saxony |
| Cyntegrity Germany GmbH | |
| CyProtect AG | Bavaria |
| Cytena 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 | |
| D+H Software GmbH | North Rhine-Westphalia |
| d-fine GmbH | |
| d-hosting GmbH | Berlin |
| D-Labs GmbH | Brandenburg |
| D-Parts Mobilphon & Zubehör GmbH | Hesse |
| d-zent Webdesign | |
| D.I.E. CAD und Statik Software GmbH | North Rhine-Westphalia |
| D.I.E. WEBexperten UG | Thuringia |
| D.Kaupke Leiterplatten Service GmbH | Bavaria |
| D.O.M. Datenverarbeitung GmbH | Bavaria |
| d.velop AG | North Rhine-Westphalia |
| D2M Summit | Bavaria |
| d3.net Internet Technologies GmbH | Bremen |
| D4L data4life gGmbH | |
| da-con GmbH | Bavaria |
| DAA GmbH | |
| Daato Technologies GmbH | |
| DAB BNP Paribas | |
| DABBEL - Automation Intelligence GmbH | |
| DaCom Database Computing GmbH | |
| Dacons UG (haftungsbeschränkt) | Baden-Württemberg |
| Daedalus | |
| daenet Gesellschaft für Informationstechnologie mbH | Hesse |
| dailyseven | Berlin |
| Daimler Fleetboard GmbH | Baden-Württemberg |
| Daimler Truck AG | |
| Dalim Software GmbH | Baden-Württemberg |
| Dalley IT | Baden-Württemberg |
| DaltaworX Software | Brandenburg |
| Damar & Hagen GmbH | Bavaria |
| damarIT - Darius Biss & Markus Heiser GbR | Lower Saxony |
| Damovo Deutschland GmbH & Co. KG | North Rhine-Westphalia |