| SiComputers | |
| Sidekick-IT | North Brabant |
| SIENN | Limburg |
| Sigmamedia.net | North Brabant |
| Signify Holding | |
| SignOn IC Trainingen | North Holland |
| SignRequest | North Holland |
| Signum Software | South Holland |
| Siilo B.V. | North Holland |
| Silicon Canals | North Holland |
| Sillar Clinical N.V. | |
| Silverflow | North Holland |
| Silverflow B.V. | |
| Simar Groep | North Holland |
| Similar.ai | |
| Simpelwerf V.O.F. | Groningen |
| Simple Analytics B.V. | |
| Single Cell Discoveries | Utrecht |
| SingularityNET | North Holland |
| SinnerG | South Holland |
| Sintermeertencollege | Limburg |
| Sioux Mathware | |
| Sioux Technologies | North Brabant |
| SIPCAPTURE | |
| Sipr | |
| SIRA | South Holland |
| Sirius B.V. | North Brabant |
| Sirius Medical Systems B.V. | |
| SISAR B.V. | |
| SiSo IT Services B.V. | Flevoland |
| Site.nu | |
| SiteBoosting | |
| Sitelight | Gelderland |
| SiteWise | Gelderland |
| Six ICT | North Brabant |
| Sixtyseven Communicatie B.V. | North Holland |
| Skalar Analytical B.V. | |
| Sketch B.V. | |
| Skikk | Overijssel |
| SkillsCV | |
| SkinVision B.V. | North Holland |
| Skoon Energy B.V. | |
| Skyberate Internet Services B.V. | Gelderland |
| Skybrokers B.V. | |
| SkylineDx B.V. | |
| SlicingPSD | North Holland |
| Slimmer | |
| SLTN | North Holland |
| Smart Event Manager | Flevoland |
| Smart Grid B.V. | |