# 2021 Braga Open – Singles

João Domingues was the defending champion but lost in the first round to Jesper de Jong.
Thiago Monteiro won the title after defeating Nikola Milojević 7–5, 7–5 in the final.

## Seeds

* Thiago Monteiro (champion)
* Taro Daniel (quarterfinals)
* Hugo Gaston (semifinals)
* Nikola Milojević (final)
* Cedrik-Marcel Stebe (quarterfinals)
* Alessandro Giannessi (second round)
* Frederico Ferreira Silva (first round)
* Steven Diez (first round, retired)

## 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

### Finals

| Semifinals | Semifinals | Semifinals | Semifinals | Final | Final | Final | Final |
| 1 | Thiago Monteiro | 6 | 6 | | | | |
| 3 | Hugo Gaston | 4 | 1 | | | | |
| 3 | Hugo Gaston | 4 | 1 | 1 | Thiago Monteiro | 7 | 7 |
| | | | | 4 | Nikola Milojević | 5 | 5 |
| 4 | Nikola Milojević | 6 | 6 | 4 | Nikola Milojević | 5 | 5 |
| Q | N Sánchez Izquierdo | 2 | 4 | | | | |

### Top half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | T Monteiro | 6 | 6 | | | | | | | | | | | | | | |
| Q | Peter Heller | 3 | 3 | | 1 | T Monteiro | 6 | 6 | | | | | | | | | |
| WC | T Cação | 4 | 6 | 6 | WC | T Cação | 1 | 1 | | | | | | | | | |
| | R Ortega Olmedo | 6 | 1 | 1 | | | | | 1 | T Monteiro | 4 | 6 | 6 | | | | |
| PR | J De Loore | 4 | 6 | 3 | | | | | | A Arnaboldi | 6 | 4 | 2 | | | | |
| | A Arnaboldi | 6 | 4 | 6 | | A Arnaboldi | 6 | 6 | | | | | | | | | |
| | T-S Kwiatkowski | 7 | 6 | | | T-S Kwiatkowski | 4 | 1 | | | | | | | | | |
| 7 | F Ferreira Silva | 5 | 3 | | | | | | | | | | | 1 | T Monteiro | 6 | 6 |
| 3 | H Gaston | 6 | 6 | | | | | | | | | | | 3 | H Gaston | 4 | 1 |
| | J Barranco Cosano | 4 | 0 | | 3 | H Gaston | 7$^7$ | 6 | | | | | | | | | |
| WC | Pedro Araújo | 6 | 6 | | WC | P Araújo | 6$^5$ | 3 | | | | | | | | | |
| WC | Luís Faria | 2 | 4 | | | | | | 3 | H Gaston | 6 | 6 | | | | | |
| | J de Jong | 6 | 6 | | | | | | | J de Jong | 3 | 1 | | | | | |
| | J Domingues | 4 | 4 | | | J de Jong | 6 | 7 | | | | | | | | | |
| Q | K Uchida | 4 | 1 | | 6 | A Giannessi | 3 | 5 | | | | | | | | | |
| 6 | A Giannessi | 6 | 6 | | | | | | | | | | | | | | |

### Bottom half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 5 | C-M Stebe | 6 | 3 | 6 | | | | | | | | | | | | | |
| | A Pellegrino | 3 | 6 | 2 | 5 | C-M Stebe | 6 | 0 | | | | | | | | | |
| | I Sijsling | 1 | 4 | | | M Vrbenský | 1 | 0$^r$ | | | | | | | | | |
| | M Vrbenský | 6 | 6 | | | | | | | 5 | C-M Stebe | 3 | 4 | | | | |
| | G Zeppieri | 4 | 4 | | | | | | | 4 | N Milojević | 6 | 6 | | | | |
| Q | S Rodríguez Taverna | 6 | 6 | | Q | S Rodríguez Taverna | 3 | 6 | 5 | | | | | | | | |
| | N Borges | 3 | 6$^6$ | | 4 | N Milojević | 6 | 3 | 7 | | | | | | | | |
| 4 | N Milojević | 6 | 7$^8$ | | | | | | | | | | | 4 | N Milojević | 6 | 6 |
| 8 | S Diez | 1$^r$ | | | | | | | | | | | | Q | N Sánchez Izquierdo | 2 | 4 |
| Q | N Sánchez Izquierdo | 2 | | | Q | N Sánchez Izquierdo | 7 | 6 | | | | | | | | | |
| | A Collarini | 6 | 6 | | | A Collarini | 5 | 2 | | | | | | | | | |
| LL | A Rybakov | 2 | 2 | | | | | | | Q | N Sánchez Izquierdo | 6 | 6 | | | | |
| | R Haase | 2 | 7$^7$ | 6 | | | | | | 2 | T Daniel | 3 | 2 | | | | |
| | R Cid Subervi | 6 | 6$^5$ | 4 | | R Haase | 3 | 1 | | | | | | | | | |
| PR | F Baldi | 2 | 6 | 0 | 2 | T Daniel | 6 | 6 | | | | | | | | | |
| 2 | T Daniel | 6 | 4 | 6 | | | | | | | | | | | | | |