| Doubles | |
|---|---|
| 2021 Zagreb Open | |
| Champions |  Evan King Hunter Reese |
| Runners-up |  Andrey Golubev Aleksandr Nedovyesov |
| Score | 6–2, 7–6(7–4) |
This was the first edition of the tournament since 2011. [1]
Evan King and Hunter Reese won the title after defeating Andrey Golubev and Aleksandr Nedovyesov 6–2, 7–6(7–4) in the final.
Andrey Golubev / Aleksandr Nedovyesov (final)
Romain Arneodo / 
Albano Olivetti (semifinals) Evan King / Hunter Reese (champions) Sadio Doumbia / Fabien Reboul (withdrew)| First round | Quarterfinals | Semifinals | Final | ||||||||||||||||||||||||
| 1 | A Golubev A Nedovyesov | 6 | 2 | [10] | |||||||||||||||||||||||
 S Báez  T Seyboth Wild | 1 | 6 | [0] | 1 | A Golubev A Nedovyesov | w/o | |||||||||||||||||||||
D Popko  A Tabilo | 4 | 6 | [10] | D Popko A Tabilo | |||||||||||||||||||||||
| N Pasha M Schnur | 6 | 1 | [7] | 1 | A Golubev A Nedovyesov | 77 | 6 | ||||||||||||||||||||
| Alt | JM Cerúndolo R Olivo |  S Walków J Zieliński | 65 | 4 | |||||||||||||||||||||||
 J Jung  G Soeda | w/o | J Jung G Soeda | 3 | 4 | |||||||||||||||||||||||
| S Walków J Zieliński | 6 | 6 | S Walków J Zieliński | 6 | 6 | ||||||||||||||||||||||
| WC |  D Golubev E Tiurnev | 0 | 2 | 1 | A Golubev A Nedovyesov | 2 | 64 | ||||||||||||||||||||
 R Jebavý  A Martin | 66 | 714 | [11] | 3 | E King H Reese | 6 | 77 | ||||||||||||||||||||
 S Balaji R Ramanathan | 78 | 612 | [9] | R Jebavý A Martin | 6 | 3 | [4] | ||||||||||||||||||||
| WC |  Z Babić  F Fallert | 77 | 4 | [8] | 3 | E King H Reese | 2 | 6 | [10] | ||||||||||||||||||
| 3 | E King H Reese | 64 | 6 | [10] | 3 | E King H Reese | 710 | 3 | [10] | ||||||||||||||||||
| WC | D Ajduković F Ninčević | 6 | 77 | 2 | R Arneodo A Olivetti | 68 | 6 | [5] | |||||||||||||||||||
F Coria  E Gómez | 3 | 62 | WC | D Ajduković F Ninčević | 5 | 4 | |||||||||||||||||||||
 L Margaroli  M Safwat | 3 | 65 | 2 | R Arneodo A Olivetti | 7 | 6 | |||||||||||||||||||||
| 2 | R Arneodo A Olivetti | 6 | 77 | ||||||||||||||||||||||||
Andrey Kuznetsov and Aleksandr Nedovyesov were the defending champions, but only Aleksandr Nedovyesov returned to defend his title, partnering up with Denys Molchanov.
Matteo Donati and Andrey Golubev beat second seeds Denys Molchanov and Aleksandr Nedovyesov 3–6, 7–6(7–5), [10–1]
This was the first edition of the tournament.
Mikhail Elgin and Yaraslav Shyla were the defending champions but chose not to defend their title.
Rameez Junaid and Purav Raja were the defending champions but lost in the quarterfinals to Andrey Golubev and Aleksandr Nedovyesov.
Gong Maoxin and Zhang Ze were the defending champions but lost in the first round to Treat Huey and Nathaniel Lammons.
Robert Galloway and Nathaniel Lammons were the defending champions but chose not to defend their title.
Andrey Golubev and Aleksandr Nedovyesov were the defending champions but chose not to defend their title.
Sekou Bangoura and Michael Mmoh were the defending champions but chose not to defend their title.
Romain Arneodo and Andrei Vasilevski were the defending champions but chose not to defend their title.
Andrey Golubev and Aleksandr Nedovyesov were the defending champions but chose not to defend their title.
Treat Huey and Nathaniel Lammons were the defending champions but chose not to defend their title.
Andrey Golubev and Aleksandr Nedovyesov were the defending champions but chose not to defend their title.
Andrey Golubev and Aleksandr Nedovyesov were the defending champions but lost in the semifinals to Szymon Walków and Jan Zieliński.
The 2021 Zagreb Open was a professional tennis tournament played on clay courts. It was part of the 2021 ATP Challenger Tour. It took place in Zagreb, Croatia between 10 and 16 May 2021.
Andrey Golubev and Aleksandr Nedovyesov were the defending champions but chose not to defend their title.
Sander Gillé and Joran Vliegen were the defending champions, but chose not to participate this year.
Evan King and Hunter Reese were the defending champions but chose not to defend their title.
Tomislav Brkić and Francisco Cabral defeated Robin Haase and Philipp Oswald in the final, 6–4, 6–4 to win the doubles tennis title at the 2022 Swiss Open Gstaad.
Ivan Dodig and Austin Krajicek defeated Nicolas Mahut and Édouard Roger-Vasselin in the final, 6–4, 7–6(7–5) to win the doubles tennis title at the 2022 Swiss Indoors.
Nicolás Jarry and Matheus Pucinelli de Almeida were the defending champions but chose not to defend their title.