| Achim Schlemmer | Baden-Württemberg |
| Achim ZWICK HR Consulting | Hamburg |
| acht und drei e.K. | |
| Achteins | Hesse |
| Acio | Lower Saxony |
| Ackee GmbH | |
| Ackermann Automation GmbH | |
| ackermann-consulting.de | North Rhine-Westphalia |
| Acolada GmbH | Bavaria |
| ACom PC | Berlin |
| Acondistec GmbH | |
| ACONI GmbH | Lower Saxony |
| Aconno GmbH | |
| Acontis Technologies GmbH | Baden-Württemberg |
| Acosoft GmbH | Saxony |
| Acotec GmbH | North Rhine-Westphalia |
| Acrolinx GmbH | |
| Acrontum GmbH | |
| ACSYS Lasertechnik GmbH | |
| ACT Angewandte Computer Technik GmbH | Schleswig-Holstein |
| act! consulting GmbH | Hamburg |
| ActeaVentures GmbH | |
| ACTech GmbH | |
| Actimage GmbH | |
| Actindo AG | Bavaria |
| Actinium Consulting GmbH | Bavaria |
| Action-Team Schön | Baden-Württemberg |
| Actisis GmbH | Rhineland-Palatinate |
| ActiTrexx GmbH | |
| Active Data | Lower Saxony |
| Active Group Gesellschaft für computergestützte Kommunikationslösungen mbH | Baden-Württemberg |
| Active Logistics AG | North Rhine-Westphalia |
| Active Online GmbH | North Rhine-Westphalia |
| Active-Websight | North Rhine-Westphalia |
| ActiveTraining | Baden-Württemberg |
| ActiveVB e.V. | North Rhine-Westphalia |
| Activeweb | Lower Saxony |
| activeWeb GmbH | Hesse |
| Activmedia.org | Bavaria |
| Activo GmbH | |
| Actiworks Application Solutions GmbH | Bavaria |
| Actome GmbH | |
| Acton Capital | |
| Acton Capital Partners GmbH | Bavaria |
| actTHweb | Lower Saxony |
| Actualize | Hesse |
| Actyx AG | |
| AcWeDeS | North Rhine-Westphalia |
| Acxiom Deutschland GmbH | Bavaria |
| Acxit Capital Holding GmbH | |