| Opus Online | |
| Organic Maps OÜ | |
| Original Games | |
| Orvium OÜ | |
| OTP | |
| Outfunnel OÜ | |
| Outvio | |
| Overall Eesti AS | Harju |
| Owlab | |
| Ownr Wallet OÜ | |
| Oyko OÜ | |
| Parasym Health | |
| Parsio | |
| Paul-Tech OÜ | |
| Paytailor | |
| Paytailor, LLC | |
| PayTraq | Harju |
| Paywerk AS | |
| Perel Eesti AS | |
| Pessimistic Security | |
| Piksel OÜ | Harju |
| Planet.ee | Harju |
| Plausible Insights OÜ | |
| Plumbr | Harju |
| Plummy Games | Harju |
| Positium | |
| Printerikskus | Harju |
| ProBit Global Services Ltd | |
| Producter | |
| Proekspert | Harju |
| ProMedia | Tartu |
| Proof Suite | |
| PROTEI | |
| Protobios | |
| QAwerk | Harju |
| Qoffer | |
| QR Menu | |
| Quantum Brain Research Institute | |
| Quppy | |
| Quppy Europe OU | Harju |
| Quretec OÜ | |
| R8 Technologies | |
| Radicenter | |
| Raison | Harju |
| Rantelon OÜ | Harju |
| Rapo | Harju |
| Rate Solutions LLC | |
| Ready Player Me | |
| RebelRoam OÜ | |
| Recoshelf | |