| Men's doubles | |||||||
|---|---|---|---|---|---|---|---|
| 2021 Belgrade Challenger | |||||||
| Final | |||||||
| Champions |  Guillermo Durán Andrés Molteni | ||||||
| Runners-up |  Tomislav Brkić Nikola Ćaćić | ||||||
| Score | 6–4, 6–4 | ||||||
| Events | |||||||
| |||||||
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This was the first of the three tournaments held in Belgrade for the 2021 tennis season. Belgrade also hosted a joint ATP/WTA tournament.
Guillermo Durán and Andrés Molteni won the title after defeating Tomislav Brkić and Nikola Ćaćić 6–4, 6–4 in the final.
Seeds
Santiago González / 
Divij Sharan (first round)
Luke Bambridge / Dominic Inglot (first round)- Tomislav Brkić / Nikola Ćaćić (final)
Nicholas Monroe / 
John-Patrick Smith (first round)
Draw
Key
- Q = Qualifier
- WC = Wild card
- LL = Lucky loser
- Alt = Alternate
- SE = Special exempt
- PR = Protected ranking
- ITF = ITF entry
- JE = Junior exempt
- w/o = Walkover
- r = Retired
- d = Defaulted
- SR = Special ranking
| First round | Quarterfinals | Semifinals | Final | ||||||||||||||||||||||||
| 1 | S González D Sharan
| 3 | 3 | ||||||||||||||||||||||||
 J Erlich A Vasilevski
| 6 | 6 | J Erlich A Vasilevski
| 6 | 6 | ||||||||||||||||||||||
L Glasspool H Heliövaara
| 6 | 4 |  A Sitak D Vega Hernández
| 1 | 1 | ||||||||||||||||||||||
| A Sitak D Vega Hernández
| 2 | 6 | J Erlich A Vasilevski
| 6 | 5 | ||||||||||||||||||||||
| 4 | N Monroe J-P Smith
| 7 | 4 | G Durán A Molteni
| 3 | 7 | |||||||||||||||||||||
| G Durán A Molteni
| 5 | 6 | G Durán A Molteni
| 6 | 6 | ||||||||||||||||||||||
 A Begemann A Vavassori
| 7 | 6 | A Begemann A Vavassori
| 2 | 4 | ||||||||||||||||||||||
| N Lammons J Withrow
| 5 | 3 | G Durán A Molteni
| 6 | 6 | ||||||||||||||||||||||
| WC | H Međedović M Topo
| 5 | 6 | 3 | T Brkić N Ćaćić
| 4 | 4 | ||||||||||||||||||||
 R Jebavý I Zelenay
| 7 | 7 | R Jebavý I Zelenay
| 6 | 3 | ||||||||||||||||||||||
| WC | V Troicki M Zekić
| 4 | 2 | 3 | T Brkić N Ćaćić
| 7 | 6 | ||||||||||||||||||||
| 3 | T Brkić N Ćaćić
| 6 | 6 | 3 | T Brkić N Ćaćić
| 6 | 7 | ||||||||||||||||||||
| WC | M Miladinović M Tepavac
| 3 | 2 | F Bagnis F Cerúndolo
| 0 | 6 | |||||||||||||||||||||
 A Göransson J O'Mara
| 6 | 6 | A Göransson J O'Mara
| 3 | 3 | ||||||||||||||||||||||
| F Bagnis F Cerúndolo
| 4 | 7 | F Bagnis F Cerúndolo
| 6 | 6 | ||||||||||||||||||||||
| 2 | L Bambridge D Inglot
| 6 | 6 | ||||||||||||||||||||||||
References
- "Ana Ivanovic to Come Out of Retirement to Play Alongside Novak Djokovic at Serbia Open". EssentiallySports. April 3, 2021.