| Cosmodata | Attica |
| Cosmolink | |
| Cosmote.gr | Attica |
| CPI Computer Peripherals International | Attica |
| Crazysoft.gr | Attica |
| Creations.gr | Attica |
| Creative People | Attica |
| CretaForce Internet Services | Attica |
| Cretan Creations | Crete |
| Crowdhackathon | Attica |
| Crypto Electronics | Attica |
| CSCartTemplates.com | Attica |
| Cube RM | Attica |
| CubeIQ Ltd | |
| Cubus Hellas Ltd | |
| cyb | Attica |
| Cyber Advertisement Team | Attica |
| Cyber PlanNet | Attica |
| Cyberlogic | |
| Cyberlogic IT & Business Consulting | Attica |
| CyberOne S.A. | |
| Cytech Ltd | Attica |
| D.D. Synergy | |
| Dabblet | Attica |
| Darkpony Ltd | Central Macedonia |
| Data and Control Systems | Attica |
| Data Communication | |
| DataSoft A.D. | Attica |
| Dataverse Ltd | |
| dbotsis | Attica |
| Deeplab.ai | |
| DEI College | Central Macedonia |
| Demo Pharmaceuticals S.A. | |
| Design Code | Attica |
| DEVit | Central Macedonia |
| deZitech Dynamics | Attica |
| Diatasys | Attica |
| Dienekis Information Systems S.A. | Attica |
| Dienergia | |
| Digimouse | |
| Digital Arts | Attica |
| Digital Challenge | Central Macedonia |
| Digital4U | |
| DigitalUp | |
| Dimicro | |
| Dimitrios Ntempos | |
| Diolkos3D | Attica |
| DNHost | Attica |
| Domi Pliroforikis | Attica |
| Dotsoft A.E. | Central Macedonia |