| Stay App | Madrid |
| Steema Software | Girona |
| StockAgile | Barcelona |
| StockCrowd | Barcelona |
| Storisell España, S.L. | |
| Stox | Barcelona |
| STR Sistemas | Madrid |
| Strands | Barcelona |
| Strata Innovation and Growth, S.L. | Madrid |
| Strategia y Kalidad GIS, S.L.U. | Madrid |
| Stratesys Technology Solutions, S.L. | Madrid |
| Stratio Big Data, Inc. | Madrid |
| STT Systems | Gipuzkoa |
| Studid DF | Girona |
| Studio Genesis | Tarragona |
| Studio128k | Córdoba |
| Suanfarma | Madrid |
| Submer | Barcelona |
| Sudespacho.net | A Coruña |
| Sulime Diseño de Soluciones, S.L. | Sevilla |
| Suministradora de Componentes Electrónicos, S.L. | Madrid |
| Sunhero Spain, S.L.U. | Barcelona |
| SunRock Biopharma | |
| Suprasys | Biscay |
| Supsonik, S.L. | Biscay |
| Sureva, S.A. | Valladolid |
| SurTel | Jaén |
| Sustonable | Valencia |
| SW Hosting & Communications Technologies, S.L. | Girona |
| sweetspot.com | Asturias |
| Sycai Medical | |
| Sycai Technologies, S.L. | Barcelona |
| Sygris | Madrid |
| Sylcom Redes y Comunicaciones | Madrid |
| Sylentis, S.A. | Madrid |
| Symanet Consultoría Informática, S.L. | A Coruña |
| Syna Therapeutics | |
| Synergy Internet, S.L. | Albacete |
| Syntax Business Solutions, S.L. | Madrid |
| Syntegon Telstar, S.L.U. | |
| Syntelix Avances Tecnológicos, S.L. | |
| Syntonize | |
| Syntra | Toledo |
| Syscad Sistemas y Servicios, S.L. | Madrid |
| Syscom Call Center Systems, S.L. | Madrid |
| Sysmex España, S.L. | Barcelona |
| Sysmo Informática, S.L. | Murcia |
| Systelec, S.A. | Madrid |
| Systeline Telecomunications, S.L. | Málaga |
| t2ó | Madrid |