| Champ: |  Roberto Carballés Baena |
| Runner: |  Damir Džumhur |
| Score: | 6–4, 7–5 |
| Before Name: | GEMAX Open – Singles |
| 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]
Roberto Carballés Baena won the title after defeating Damir Džumhur 6–4, 7–5 in the final.