| SigmaNet | Mureș |
| Sigtree | |
| Silkweb | Maramureș |
| Sim Soft Distribution S.R.L. | Cluj |
| Simion Stoilow Institute of Mathematics of the Romanian Academy | Bucharest |
| SimpliQ S.R.L. | Cluj |
| Sintec S.R.L. | Maramureș |
| SIS | Bucharest |
| SisleyStudio | Sibiu |
| Site Expert | Bucharest |
| SiteuriWeb | Bucharest |
| SiteXDesign | Iași |
| SIVECO Romania | Bucharest |
| Sky Group | Timiș |
| Sky Soft S.R.L. | |
| Smarsoft Electronic S.R.L. | |
| Smart Computers Iasi | Iași |
| Smart Id Dynamics S.A. | Bucharest |
| Smart Media Interactive S.R.L. | Argeș |
| Smart Protection | |
| Smart Recruit | |
| Smart-hosting.ro | Satu Mare |
| Smart-X Net Apps | |
| Smartart | Sibiu |
| SmartBill | Sibiu |
| SmartDreamers | Bucharest |
| SmartFotovoltaic | |
| Smartnews | Mureș |
| SmartPoint Consulting | |
| Smartree Romania | Bucharest |
| SmartSpot | |
| SmartSystems | Bucharest |
| SmartTel | |
| Smith&Smith | |
| SOBIS Solutions S.R.L. | Bucharest |
| Soft & Service | |
| Soft Dreams | |
| Soft Expert | |
| Soft Ground | |
| Soft Net Consulting | |
| Soft Pepper Solutions | |
| Soft Systems | |
| Soft Tehnica | |
| Soft112 | Cluj |
| Soft32 | Sibiu |
| Soft82 | Constanța |
| Softbinator Technologies | |
| Softeconomic | |
| Softeh Plus S.R.L. | Bucharest |
| Softelligence | |