| SCIA N.V. | Limburg |
| Science Parks of Wallonia | Namur |
| Sciensano | |
| SCK CEN | |
| ScriptBook N.V. | Antwerp |
| SDP | East Flanders |
| SEE Telecom | Walloon Brabant |
| Seety | |
| Segments.ai | |
| SeJo IT | |
| Selection Computer Distribution | Brussels-Capital |
| Selligent | Walloon Brabant |
| Sematix IT Services | Hainaut |
| Sensifai | Brussels-Capital |
| Sensolus | |
| Sentiance N.V. | |
| SEO Dreams | Antwerp |
| Seodvize B.V.B.A. | West Flanders |
| Septentrio | |
| Sequana Medical N.V. | |
| Serico Solutions | |
| ServersCheck B.V. | Walloon Brabant |
| Service de médiation pour les télécommunications | Brussels-Capital |
| Services Informatiques pour Professionnels | Hainaut |
| Servico B.V.B.A. | Antwerp |
| Servilux | Limburg |
| SettleMint | |
| Sewan Groupe | |
| Sgraffit | Hainaut |
| Shaping Europe’s digital future | |
| Shayp S.A. | |
| Shown | |
| Showpad | East Flanders |
| Shyfter S.A. | |
| Sigasi nv | East Flanders |
| SigmaConso | Brussels-Capital |
| Sign2Pay.com N.V. | |
| Silex Insight | Walloon Brabant |
| Silverfin | East Flanders |
| Silverfin | |
| Simac | Flemish Brabant |
| SimpleBackups | |
| Sipro Media B.V. | Flemish Brabant |
| Sirris | Antwerp |
| Site2host | West Flanders |
| SiteDev | East Flanders |
| Siteffect | Flemish Brabant |
| SiteHosting | East Flanders |
| SiteManager | |
| Sitemark | |