| Champ: | Hugo Nys Tim Pütz |
| Runner: |  Luke Bambridge Dominic Inglot |
| Score: | 7–5, 3–6, [10–3] |
| Type: | singles doubles |
| Before Year: | 2019 |
Hugo Nys and Tim Pütz defeated Luke Bambridge and Dominic Inglot in the final, 7–5, 3–6, [10–3], to win the doubles tennis title at the 2021 Estoril Open. It was Nys and Pütz's first title as a team in their second tournament together on the ATP Tour, marking Nys's second and Pütz's third individual career tour-level doubles titles. Bambridge and Inglot were in contention for their first title as a team after reaching their first tour-level final without dropping a set.[1]
Jérémy Chardy and Fabrice Martin were the defending champions from when the tournament was last held in 2019,[2] but Chardy did not return to compete. Martin played alongside Édouard Roger-Vasselin but lost in the first round to Cristian Garín and David Vega Hernández.[3]