| DMEXCO | North Rhine-Westphalia |
| DMK E-Business GmbH | Berlin |
| DMKZWO GmbH & Co. KG | North Rhine-Westphalia |
| dmmd GmbH & Co. KG | Lower Saxony |
| dmp webbau media GmbH | |
| DMRZ Deutsches Medizinrechenzentrum GmbH | North Rhine-Westphalia |
| DMS Daten Messen Software Waagen Doris Schröer e.K. | North Rhine-Westphalia |
| DMS Direkt Marketing Services GmbH | |
| DMS-SYSTEMHAUS Gesellschaft für EDV-Lösungen mbH | Bavaria |
| DN-Computersysteme | Bavaria |
| DN-Systems Enterprise Internet Solutions GmbH | Lower Saxony |
| DNS Datentechnik, Netzwerk und Systemhaus GmbH | Saxony-Anhalt |
| DNSNET | Berlin |
| DNTOX GmbH | |
| DO-net GmbH | North Rhine-Westphalia |
| do.de | Lower Saxony |
| DOAG Dienstleistungen GmbH | Berlin |
| DOBBERTIN Industrie-Elektronik GmbH | Baden-Württemberg |
| DOBRICK+WAGNER SOFTWAREHOUSE GMBH | North Rhine-Westphalia |
| Dobrick.com Softwareentwicklung GmbH | Hamburg |
| DocCheck agency AG | |
| DocCheck Guano AG | |
| Dochouse GmbH | Baden-Württemberg |
| Docs in Clouds GmbH | |
| Doctorly GmbH | |
| DocuMix GmbH | Hesse |
| DocuServe Vertriebs GmbH | Bavaria |
| Dodona Database Consulting | North Rhine-Westphalia |
| DOGA Steuerungstechnik GmbH | North Rhine-Westphalia |
| dogado GmbH | North Rhine-Westphalia |
| Dogo App UG | Berlin |
| doIT Solutions GmbH | |
| Dokay GmbH | Baden-Württemberg |
| Dokumenten- und Datenservice Wandel GmbH | Baden-Württemberg |
| Dolosys GmbH | |
| DOM Digital Online Media GmbH | |
| DomainFactory GmbH | Bavaria |
| DomainProvider.de | North Rhine-Westphalia |
| Domainregistry.de | North Rhine-Westphalia |
| Domeba GmbH | Saxony |
| Domke Consulting | Hesse |
| DOMUS Software AG | Bavaria |
| Donner & Reuschel AG | |
| Donner + Partner GmbH Bildungszentren | |
| doo GmbH | Bavaria |
| doob SE | |
| Door2Door GmbH | |
| Doozer | Berlin |
| doppelt.digital | |
| doQtor GmbH | |