| Sociality | |
| Soft Design | |
| Softly | |
| Software Competitiveness International S.A. | Attica |
| Softways A.E. | Attica |
| SOFTWeb I.T. Solutions | Attica |
| Solidus Fiscal Systems Ltd | |
| SOTIRIA Technology | |
| SourceLair Ltd | Attica |
| South-East European Research Centre | |
| Spartan Software | Peloponnese |
| SSMART S.A. | Attica |
| Standard Data | |
| Starttech Ventures | |
| Startup Europe | |
| Startup Greece | Attica |
| Startup Nation | |
| Startup.gr | Attica |
| Startupper | Attica |
| Steficon S.A. | Attica |
| Sterigma Ltd | Attica |
| Stevy | Attica |
| Sxolinux | Attica |
| Symbol Co. | Attica |
| Synergic Software | Attica |
| SYNPAN Software | Attica |
| SYNTAX IT, Inc. | Attica |
| System S.A. | Attica |
| Systematics A.E. | |
| SYSTEMIC RM Single Member S.A. | Attica |
| Taneo S.A. | Attica |
| Task Hellas | Attica |
| TechCubed | |
| TechGroup Ltd | |
| Technical University of Crete | |
| Technical University of Crete - Department of Electronic & Computer Engineering | Crete |
| Technicomer S.A. | |
| Technologismiki | Attica |
| Technopolis s.a. | Attica |
| TechPals | |
| TECHTRON Technical & Commercial p.c.c. | |
| TechValue.gr | |
| Tefter.io | |
| TeleActive Τηλεπικοινωνίες | Attica |
| Teletel S.A. | Attica |
| Tellody | Attica |
| Terracom S.A. | |
| TESAgroup | Attica |
| Tessera Multimedia | Attica |
| Texnikoi.com | Attica |