| AreTheyHappy N.V. | |
| Argon7 | Walloon Brabant |
| Arkance Systems | East Flanders |
| ArKaos | Walloon Brabant |
| Arkite | |
| Arpaweb | Namur |
| Arpege Music | |
| Art Vision International BVBA | Antwerp |
| Arteïa | |
| Artialis S.A. | |
| ArtiQ | |
| ArtWhere | Walloon Brabant |
| ASCI N.V. | East Flanders |
| ASP | Brussels-Capital |
| Assusoft | |
| ASTRID | Brussels-Capital |
| AstriVax | |
| Athena Computer Services | Liège |
| ATiT Audiovisual Technologies, Informatics and Telecommunications | Flemish Brabant |
| ATM-PRO | Walloon Brabant |
| Atomikos B.V.B.A. | Antwerp |
| Aucenanne | Hainaut |
| Audaxis | Walloon Brabant |
| Augustine Therapeutics | |
| Aurelium | Antwerp |
| Automation N.V. | Flemish Brabant |
| Autorité de la protection des données | Brussels-Capital |
| Autorité des services et marchés financiers | |
| AvioBook | |
| Aware N.V./S.A. | |
| Awell | |
| Axiles Bionics | |
| AxonJay | |
| AxonJay | |
| B & F | Brussels-Capital |
| B&B Computer Solutions | Walloon Brabant |
| B-Sprouts | |
| B-U-T N.V. | Antwerp |
| B-Webdesign | East Flanders |
| B. Rekencentra N.V. | Antwerp |
| BA N.V. | Flemish Brabant |
| Babelway S.A./N.V. | Walloon Brabant |
| Backoffice Europe | Antwerp |
| BakerMEN N.V. | Antwerp |
| BAN Flanders | |
| Bandito Studio | Hainaut |
| Bank Van Breda | Antwerp |
| Barclaey, Inc. | Antwerp |
| Bausch Datacom | Flemish Brabant |
| BBI Solutions | |