2021 Mutua Madrid Open – Men's doubles

Marcel Granollers and Horacio Zeballos defeated Nikola Mektić and Mate Pavić in the final, 1–6, 6–3, [10–8], to win the men's doubles tennis title at the 2021 Madrid Open. It was the third-seeded duo's third ATP Tour Masters 1000 doubles title together. Mektić and Pavić were contending to be the first doubles team in five years to win a season's first three Masters 1000 events.

Jean-Julien Rojer and Horia Tecău were the defending champions from when the tournament was last held in 2019, though they returned to defend their title with different partners. Rojer partnered with Marcelo Melo but lost in the second round to Tim Pütz and Alexander Zverev. Tecău partnered with Kevin Krawietz and lost to Ivan Dodig and Filip Polášek, also in the second round.

Pavić and Robert Farah were in contention for the ATP No. 1 doubles ranking at the start of the tournament. Pavić retained the top ranking after Farah lost in the second round.

Seeds
The top four seeds received a bye into the second round. • # 🇨🇴 Juan Sebastián Cabal / 🇨🇴 Robert Farah (second round)

• # Nikola Mektić / Mate Pavić (final)

• # 🇪🇸 Marcel Granollers / 🇦🇷 Horacio Zeballos (champions)

• # Ivan Dodig / 🇸🇰 Filip Polášek (quarterfinals)

• # 🇺🇸 Rajeev Ram / 🇬🇧 Joe Salisbury (first round)

• # 🇫🇷 Pierre-Hugues Herbert / 🇫🇷 Nicolas Mahut (quarterfinals)

• # Wesley Koolhof / 🇵🇱 Łukasz Kubot (quarterfinals)

• # 🇬🇧 Jamie Murray / 🇧🇷 Bruno Soares (first round)

Seeds

 * Rankings are as of April 26, 2021.

Other entrants
The following pairs received wildcards into the doubles main draw: The following pair received entry into the doubles draw as alternate:
 * 🇪🇸 Alejandro Davidovich Fokina / 🇪🇸 Fernando Verdasco
 * 🇪🇸 Marc López / 🇪🇸 Jaume Munar
 * Petros Tsitsipas / Stefanos Tsitsipas
 * Raven Klaasen / 🇯🇵 Ben McLachlan

Withdrawals

 * Before the tournament
 * Borna Ćorić / Franko Škugor → replaced by 🇭🇺 Márton Fucsovics / 🇳🇴 Casper Ruud
 * 🇪🇸 Alejandro Davidovich Fokina / 🇪🇸 Fernando Verdasco → replaced by Raven Klaasen / 🇯🇵 Ben McLachlan