| ServiNetwork, S.C.P. | Barcelona |
| Serviport Andalucía, S.A. | Sevilla |
| ServiTux | Alicante |
| Setecem | Barcelona |
| Setting Consultoria | Barcelona |
| Sewan | Madrid |
| SG Multimèdia | Barcelona |
| Shakers | |
| Sheetgo | Valencia |
| Ship2B Foundation | Barcelona |
| Shopery | Barcelona |
| SHS Consultores | Sevilla |
| Sicaman Nuevas Tecnologías, S.L. | Ciudad Real |
| SicaSoft | Madrid |
| Sicat Sistemes d'Informació, S.L. | Barcelona |
| Siddex | Valladolid |
| Siemanet, S.L. | Málaga |
| Siemens Gamesa Renewable Energy, S.A. | Biscay |
| Sigma Data Services | Madrid |
| Signaturit | Barcelona |
| Signia | Barcelona |
| SII Concatel | Barcelona |
| SiiNet.com | Madrid |
| SILEX Informática, S.L. | Barcelona |
| Silicon Spain | Madrid |
| SILvia Aplicaciones de Gestión | |
| SIM Levante | Valencia |
| SIMA Informática | Álava |
| SimbioWork | Sevilla |
| SIMM Informatica | A Coruña |
| Simple Soluciones Informáticas, S.L. | Madrid |
| SimpleCloud | Valencia |
| Simply Recovery | Biscay |
| SimplySoft | Barcelona |
| Simpple | Tarragona |
| Simsa | Barcelona |
| SincroPool | |
| Sinetric Systems, S.L. | Barcelona |
| Singular | Madrid |
| Singular Bank, S.A.U. | |
| Singular Cover SBF | Barcelona |
| SingularBrain | Asturias |
| SingularCover | Barcelona |
| Sinis Technology | Madrid |
| Sintelec Informática, S.L. | Barcelona |
| Sion Certifications, S.L. | Madrid |
| Sipay Plus, S.L. | Madrid |
| Sirocco Energy, S.L. | Madrid |
| SIRT | Barcelona |
| SISCAPP Comunicaciones, S.L. | Madrid |