| Champ: |  Guillermo Durán Andrés Molteni |
| Runner: |  Tomislav Brkić Nikola Ćaćić |
| Score: | 6–4, 6–4 |
| Before Name: | GEMAX Open – Doubles |
| Before Year: | 2010 |
| Main Name: | GEMAX Open |
See main article: 2021 Belgrade Challenger.
This was the first of the three tournaments held in Belgrade for the 2021 tennis season. Belgrade also hosted a joint ATP/WTA tournament.[1]
Guillermo Durán and Andrés Molteni won the title after defeating Tomislav Brkić and Nikola Ćaćić 6–4, 6–4 in the final.