| AST GmbH | Baden-Württemberg |
| ASTA-PICCA IT-Systeme GmbH | Saxony |
| asterisk-berlin | Berlin |
| Astraia Software GmbH | Bavaria |
| Astrotel Internetmarketing GmbH | Brandenburg |
| ASTUTIA Ventures GmbH | Bavaria |
| ASTUTIA Ventures GmbH | |
| Asura Technologies Ltd | |
| Asuro GmbH | Hesse |
| Asvin.io | |
| ASVOR Software | North Rhine-Westphalia |
| AT&M Technologie und Marketing GmbH | Thuringia |
| AT+C EDV GmbH | |
| at2 GmbH | Bavaria |
| atai Life Sciences N.V. | |
| ATARI Bit Byter User Club e.V. | North Rhine-Westphalia |
| ATB Blank GmbH | Bavaria |
| ATB – Institut für angewandte Systemtechnik Bremen GmbH | |
| atbit Bremer Innovations-und Technologiegesellschaft mbH | Bremen |
| AtBits GmbH & Co. KG | Baden-Württemberg |
| ATCOM Datensysteme GmbH | North Rhine-Westphalia |
| ATE Software GmbH | Hesse |
| Atec GmbH | Baden-Württemberg |
| Ateco EDV GmbH | Hesse |
| Atelier für Mediengestaltung Doering, Kern, Günther GbR | North Rhine-Westphalia |
| Atelier Vision | Baden-Württemberg |
| AtelierHB9 | Berlin |
| Atesio GmbH | Berlin |
| Atheneum Partners | |
| Atino GmbH | North Rhine-Westphalia |
| Atip GmbH | Hesse |
| ATIS systems GmbH | Hesse |
| Atix AG | Bavaria |
| ATK WebDesign | Berlin |
| ATK-WebDesign | Berlin |
| atlan-tec Systems GmbH | North Rhine-Westphalia |
| Atlantic Labs Manager GmbH | |
| Atlantik Networxx GmbH | |
| ATLAS Biolabs GmbH | |
| Atlas Metrics | |
| Atlas-Elektronik GmbH | Bremen |
| ATLAS.ti Scientific Software Development GmbH | Berlin |
| Atlatec | Baden-Württemberg |
| ATM ComputerSysteme GmbH | |
| ATMedia GmbH | Saarland |
| ATMOS Space Cargo GmbH | |
| ATO interactive GmbH | |
| Atolls GmbH | |
| Atomtigerzoo | North Rhine-Westphalia |
| Atopia Space GmbH | |