| Assedo | Rhineland-Palatinate |
| Assembler ASM | Berlin |
| Assetizr | |
| AssetMetrix GmbH | |
| AsSign Consulting GmbH | |
| Assistra Cloud Services GmbH | Bavaria |
| ASSMANN Electronic GmbH | North Rhine-Westphalia |
| Assmy & Böttger Electronic GmbH & Co. KG | Lower Saxony |
| AST GmbH | Baden-Württemberg |
| ASTA-PICCA IT-Systeme GmbH | Saxony |
| asterisk-berlin | Berlin |
| Astos Solutions | |
| Astraia Software GmbH | Bavaria |
| Astro-und Feinwerktechnik Adlershof GmbH | |
| Astrotel Internetmarketing GmbH | |
| ASTRUM IT GmbH | |
| ASTUTIA Ventures GmbH | |
| Asura Technologies Ltd | |
| Asuro GmbH | Hesse |
| Asvin.io | |
| ASVOR Software | North Rhine-Westphalia |
| Asylum Square Interactive GmbH | |
| AT&M Technologie und Marketing GmbH | Thuringia |
| AT+C EDV GmbH | |
| at2 GmbH | Bavaria |
| atac | |
| 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 |
| aTENSION.life GmbH | |
| 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 | |