| Seris Konsalnet Holding S.A. | |
| Serv-net | |
| ServoCode Sp. z o.o. | |
| Servodata Elektronik Sp. z o.o. | Lublin |
| Serwis komputerowy | Masovian |
| Serwis komputerowy Olsztyn | Warmian-Masurian |
| Serwis.eu | |
| Serwnet | Masovian |
| Seth Software Sp. z o.o. | |
| Setia.pl | Silesian |
| Sevenet S.A. | Masovian |
| SFT Computers | |
| Sgiti | Pomeranian |
| SGPR.TECH | |
| Shape.Care Sp. z o.o. | |
| Shaped Thoughts Sp. z o.o. | |
| Shapespark Sp. z o.o. | |
| ShareSpace | |
| Sharp Electronics CEE | Masovian |
| SharpAI | |
| ShelfWise Sp. z o.o. | |
| Shift-Systemy Komputerowe Sp. J. | Lesser Poland |
| Shock IT Sp. z o.o. | |
| Shoper S.A. | Lesser Poland |
| Shoplo Sp. z o.o. | Masovian |
| Si-Consulting Sp. z o.o. | Lower Silesian |
| Sidnet Solutions Sp. z o.o. | |
| Sieć Badawcza Łukasiewicz - Instytut Techniki i Aparatury Medycznej | |
| Sieć Badawcza Łukasiewicz - Poznański Instytut Technologiczny | |
| Sieć Badawcza Łukasiewicz - Przemysłowy Instytut Automatyki i Pomiarów PIAP | |
| Sieci Blokowe | Świętokrzyskie |
| SIETOM Sp. z o.o. | Pomeranian |
| Sigma Connectivity Sp. z o.o. | |
| Sii Sp. z o.o. | |
| Silk Data Sp. z o.o. | |
| Silk Software House Sp. z o.o. | Masovian |
| SilkPLM | |
| Silnet Media | |
| Siltec Sp. z o.o. | Masovian |
| Silver Fox S.C. | |
| Simpl sp. z o.o. | Lesser Poland |
| Simple S.A. | Masovian |
| SimpleLocalize | |
| Sinova Development | |
| Sinterit Sp. z o.o. | |
| Sintra | |
| SIRC Sp z o.o. | |
| Sirocco Mobile Sp. z o.o. | |
| SIRTEL Sp. z o.o. | Masovian |
| SISCO Sp. z o.o. | Łódź |