| Tellweb Internet-Service GmbH | North Rhine-Westphalia |
| telos Systementwicklung GmbH | Hamburg |
| Telroth GmbH | North Rhine-Westphalia |
| TELTEC Semiconductor Technic GmbH | Baden-Württemberg |
| TELUM GmbH | |
| Tema GmbH & Co. KG | Baden-Württemberg |
| Temeco IT- &Personalservices Peter Biebow e.K. | |
| Temedica GmbH | |
| TeMeno GmbH | North Rhine-Westphalia |
| Temicon GmbH | |
| Tempowerk | |
| Tempr.email | Saxony |
| TEMPTON Verwaltungs GmbH | North Rhine-Westphalia |
| Ten Eyes media | |
| TEN IT GmbH | |
| Tenios GmbH | North Rhine-Westphalia |
| TenMedia GmbH | |
| TentaConsult Pharma & Med GmbH | |
| Tenzir | |
| Teqcycle Solutions GmbH | Bavaria |
| TEQneers GmbH & Co. KG | Baden-Württemberg |
| Tera IT Solutions GmbH | |
| TERA Kommunalsoftware GmbH | Bavaria |
| Teracue GmbH | Bavaria |
| Teraki GmbH | Berlin |
| teraone | |
| Teratis Solutions GmbH | |
| Terms-Produkten | |
| Terra One Climate Solutions GmbH | |
| Terra-web | |
| terra.berlin | Berlin |
| TERRACS - die Welt von Internet & GIS | Baden-Württemberg |
| terradoor | Berlin |
| terralink networks GmbH | Hamburg |
| TerraYou GmbH | |
| Territorium Online GmbH | Baden-Württemberg |
| Territory | |
| TES Electronic Solutions GmbH | Baden-Württemberg |
| Tesat-Spacecom GmbH & Co. KG | Baden-Württemberg |
| Testa GmbH | Bavaria |
| testerpool UG (haftungsbeschränkt) | |
| TestingSolutions GmbH & Co. KG | Bavaria |
| TestSolutions GmbH | |
| Testwerk Ihr Elektronik-Prüfcenter e.K. | Hamburg |
| testxchange GmbH | |
| TETRA Computersysteme GmbH | North Rhine-Westphalia |
| Teubner Industrie-Elektronik GmbH | |
| teuto.net Netzdienste GmbH | Hesse |
| Tevitel AG | Berlin |
| Tews Technologies GmbH | Schleswig-Holstein |