| TU Clausthal Insitut für Informatik | Lower Saxony |
| Tubepharma | |
| Tubulis GmbH | |
| Tucan.ai GmbH | |
| Tucana Handels GmbH | Hesse |
| Tuesday Coworking | Berlin |
| Tulock GmbH | Saarland |
| Tumbov Software | Baden-Württemberg |
| Turck duotec GmbH | North Rhine-Westphalia |
| TurnFriendly Software GmbH | Bavaria |
| Tuta | |
| Tutech Innovation GmbH | |
| Tutego | North Rhine-Westphalia |
| Tutum GmbH | Bavaria |
| TÜV Informationstechnik GmbH | North Rhine-Westphalia |
| TÜV NORD AG | Lower Saxony |
| TÜV SÜD AG | |
| Tuxedo Computers | Bavaria |
| Tuxguard Technology e.K. | Saarland |
| Tuxpost | Berlin |
| Tvarit GmbH | |
| TVM Capital GmbH | Bavaria |
| TVS IT-Systeme GmbH | |
| Twago | Berlin |
| TWAICE | |
| Twain Technology UG (haftungsbeschränkt) | |
| Twenty Billion Neurons GmbH | Berlin |
| TWENTY4HOURS e.K. | North Rhine-Westphalia |
| Twinsity GmbH | |
| Twinsoft GmbH & Co. KG | Hesse |
| twinwin GmbH | |
| Twire GmbH | |
| Twostay UG (haftungsbeschränkt) | |
| twosteps GmbH | Baden-Württemberg |
| TWT GmbH | Baden-Württemberg |
| TWT Online Marketing GmbH | North Rhine-Westphalia |
| TWT reality bytes GmbH | North Rhine-Westphalia |
| TX Kommunikationsgesellschaft mbH | Baden-Württemberg |
| Tyclipso.net | Saxony |
| Tylers Agency GmbH | |
| Typework | Bavaria |
| TYPO3 Akademie | Bavaria |
| TYPO3 Blogger | North Rhine-Westphalia |
| TYPO3 Videos | Schleswig-Holstein |
| TYPO3 Web Sites | Schleswig-Holstein |
| TYPO3-Hilfe | Schleswig-Holstein |
| Typo3.net | North Rhine-Westphalia |
| TYPO34u | Bavaria |
| TYPO3erweiterungen.de | Bavaria |
| Typografie.info | Thuringia |