| Champ: | Nikola Mektić Mate Pavić |
| Runner: |  Rajeev Ram Joe Salisbury |
| Score: | 6–4, 7–6(7–4) |
| Before Name: | Italian Open – Men's doubles |
| After Name: | Italian Open – Men's doubles |
See main article: article and 2021 Italian Open (tennis).
Nikola Mektić and Mate Pavić defeated Rajeev Ram and Joe Salisbury in the final, 6–4, 7–6(7–4), to win the men's doubles tennis title at the 2021 Italian Open. The second seeds did not drop a set en route to their third ATP Tour Masters 1000 victory together and their sixth title overall of the season. The all-Croatian pair also became the second doubles team to have reached the finals of the first four Masters 1000 tournaments in a season after the Bryan brothers, who last accomplished the feat in 2018. Ram and Salisbury were competing for their first title of the season and their fourth title together.[1] [2]
Marcel Granollers and Horacio Zeballos were the defending champions,[3] but they lost in the quarterfinals to Ram and Salisbury.[4]
The following pairs received wildcards into the doubles main draw:
Marco Cecchinato / Stefano Travaglia Fabio Fognini / Lorenzo Musetti Lorenzo Sonego / Andrea VavassoriThe following pairs received entry into the doubles main draw as alternates:
Gonzalo Escobar Liam Broady / Andy Murray
Félix Auger-Aliassime / 
Hubert Hurkacz → replaced by Liam Broady / Andy Murray
Márton Fucsovics / 
Casper Ruud → replaced by Marcelo Arévalo / Matwé Middelkoop
Karen Khachanov / Andrey Rublev → replaced by Petros Tsitsipas / Stefanos Tsitsipas Gonzalo Escobar
Colombia
Slovakia
Spain
Argentina
Brazil
Romania