| CostPocket | |
| Coverler | |
| Crespect OÜ | |
| CRM Süsteemid OÜ | Harju |
| Crowdestor | |
| Crowdin | |
| Crypt.ee | |
| Crystalspace OÜ | Tartu |
| Customer.guru | |
| Cyberarch Consulting | Harju |
| CyberLab.Team OÜ | Harju |
| Cyberlands.io OÜ | |
| Cybernetica | Harju |
| CYBERS | |
| CybExer Technologies | |
| Cyphergram | |
| Daniliants Ventures OÜ | |
| Dashbird | |
| Dashbouquet Development, LLC | |
| Data Service OÜ | Harju |
| Data-Xata | Harju |
| DataCatering OÜ | Harju |
| DataCumulus OÜ | |
| Datafox | |
| Datagate Arvutid | Harju |
| DataGates Group OÜ | Harju |
| Datami | |
| Datasec OÜ | Harju |
| Datastake | |
| DBWeb | |
| Deaction | Harju |
| Dealum OÜ | |
| Dedicatted | |
| DeepBurner | Harju |
| DEIP | |
| Deltmar OÜ | Harju |
| DesignFirst | |
| Dev.family OÜ | Harju |
| Develop | Harju |
| DevGame OÜ | |
| Devsoft Baltic OÜ | |
| Devtailor | |
| DevTernity OÜ | |
| DevTraining | |
| DigiDeli | Harju |
| Digimaja | |
| Digimarket OÜ | Harju |
| Digipal | |
| Digipurk OÜ | |
| DigiSoov OÜ | |