| Cream Software | Lesser Poland |
| CreamFinance Poland Sp. z o.o. | |
| createIT | |
| Createsoft | Świętokrzyskie |
| Creativ24 | |
| Creotech Instruments S.A. | |
| CRLAB | Lower Silesian |
| CRN Polska | Masovian |
| Crocoders | |
| CROS CRO Sp. z o.o. | |
| CROSS | |
| Crossweb | Lesser Poland |
| CrustLab | |
| Cryptiony R&D Sp. z o.o. | |
| Cryptomage S.A. | |
| CryptoTech P. S.A. | |
| CS-Lab s.c. | Kuyavian-Pomeranian |
| CSHARK Sp. z o.o. | |
| CSS Peeper | |
| CTHINGS.CO Sp. z o. o. | |
| CTHINGS.co Sp. z o.o. | |
| Cube Group S.A. | Masovian |
| CubeMatic | Masovian |
| Cubesoft | |
| Curcuma | Łódź |
| Curiosum Sp. z o.o. | |
| Currency One S.A. | |
| Cut2Code | Lower Silesian |
| Cutt.ly | |
| Cyber Security Lab Sp. z o.o. | |
| Cyberbajt | Lublin |
| Cybernet-Soft | |
| CyberRescue Sp. z o.o. | |
| Cybersecurity Studio Sp. z o.o. | Subcarpathian |
| Cyberstudio Sp. z o.o. | Silesian |
| cyberstudio Sp. z o.o. | |
| Cyberus Labs | |
| cyber_Folks S.A. | |
| Cyfral Chabelska i Wspólnicy Sp.J. | Łódź |
| Cyfronet, Akademickie Centrum Komputerowe AGH w Krakowie | Lesser Poland |
| Cyfrowe Centrum Serwisawe S.A. | Masovian |
| Czek.it | |
| Czysta3.vc Sp. z o.o. | |
| D3M.pl | Świętokrzyskie |
| Da Vinci Studio | |
| DAC S.A. | Pomeranian |
| DAC.digital | |
| DACPOL Sp. z o.o. | Masovian |
| Daftcode | |
| Dailyweb.pl | |