| Allied for Startups | Brussels-Capital |
| ALLOcloud | |
| Allrounders Webdesign | Antwerp |
| AllThingsTalk N.V. | |
| AlmightyDomains | East Flanders |
| Alpha Electronics Europe S.A. | Walloon Brabant |
| AlphaZip | West Flanders |
| altavia.belgium | |
| AlterEyes N.V. | |
| Alterezo | Liège |
| Alterfin | |
| Altheria Solutions S.R.L. | |
| Alys S.P.R.L. | Brussels-Capital |
| Amaranthe Web Agency S.P.R.L. | Namur |
| Amazing Things | East Flanders |
| Ambugest | Namur |
| Amista | |
| Ampacimon | |
| AmphiStar Biosurfactants | |
| AMS Robotics | |
| Amyl Therapeutics | |
| Anacura | |
| Anais Digital | |
| Androme | Limburg |
| ANeuroTech | |
| Angel.me | |
| Antenor Payment Systems N.V. | Antwerp |
| Antleron | |
| Antoine Cailliau | Walloon Brabant |
| Antoine Potten | |
| Antwerp Management School | |
| Antwerp Maritime Academy | |
| Antwerp Space | |
| Anubex N.V. | Antwerp |
| AnySite | East Flanders |
| AnySurfer | Brussels-Capital |
| AP Hogeschool Antwerpen | |
| Apaxen | |
| Aphea.Bio | |
| Apicbase N.V. | Antwerp |
| Appart Agency | |
| Appdnd | |
| AppFoundry | Antwerp |
| Applied Maths N.V. | East Flanders |
| Appmiral | |
| Apprends LaTeX | |
| Approach Belgium S.A./N.V. | Walloon Brabant |
| AppTweak | |
| Aprico Consultants N.V./S.A. | Flemish Brabant |
| Aptec Diagnostics | |