| Doubles | |
|---|---|
| 2021 Open de Oeiras | |
| Champions |  Mats Moraing Oscar Otte |
| Runners-up |  Riccardo Bonadio  Denis Yevseyev |
| Score | 6–1, 6–4 |
This was the first of four editions of the tournament in the 2021 ATP Challenger Tour calendar. [1]
Mats Moraing and Oscar Otte won the title after defeating Riccardo Bonadio and Denis Yevseyev 6–1, 6–4 in the final.
Enzo Couacaud / Manuel Guinard (quarterfinals)
Sergio Galdós / 
Sergio Martos Gornés (first round)
Elliot Benchetrit / 
Zdeněk Kolář (quarterfinals)
Gonçalo Falcão / Gonçalo Oliveira (quarterfinals)| First round | Quarterfinals | Semifinals | Final | ||||||||||||||||||||||||
| 1 | E Couacaud M Guinard | 6 | 6 | ||||||||||||||||||||||||
| WC | Pedro Araújo T Cação | 0 | 3 | 1 | E Couacaud M Guinard | 3 | 6 | [5] | |||||||||||||||||||
| Alt |  H Bourchier  K Uchida | 4 | 3 |  T Gabashvili  C-h Tseng | 6 | 2 | [10] | ||||||||||||||||||||
| T Gabashvili C-h Tseng | 6 | 6 | T Gabashvili C-h Tseng | 2 | 3 | ||||||||||||||||||||||
| 3 | E Benchetrit Z Kolář | 6 | 77 | R Bonadio D Yevseyev | 6 | 6 | |||||||||||||||||||||
| WC | F Cabral Luís Faria | 3 | 65 | 3 | E Benchetrit Z Kolář | 77 | 3 | [8] | |||||||||||||||||||
 H Johnson Y Johnson | 7 | 4 | [3] | R Bonadio D Yevseyev | 63 | 6 | [10] | ||||||||||||||||||||
| R Bonadio D Yevseyev | 5 | 6 | [10] | R Bonadio D Yevseyev | 1 | 4 | |||||||||||||||||||||
 A Collarini GM Moroni | 4 | 4 | M Moraing O Otte | 6 | 6 | ||||||||||||||||||||||
| M Moraing O Otte | 6 | 6 | M Moraing O Otte | 6 | 6 | ||||||||||||||||||||||
E Escobedo  V Orlov | 4 | 4 | 4 | G Falcão G Oliveira | 3 | 2 | |||||||||||||||||||||
| 4 | Gonçalo Falcão G Oliveira | 6 | 6 | M Moraing O Otte | 6 | 3 | [10] | ||||||||||||||||||||
 L Miedler  N Serdarušić | 6 | 6 | L Miedler N Serdarušić | 4 | 6 | [8] | |||||||||||||||||||||
| WC | Miguel Gomes H Rocha | 3 | 1 | L Miedler N Serdarušić | 6 | 6 | |||||||||||||||||||||
| P Kotov A Vatutin | 6 | 6 | P Kotov A Vatutin | 4 | 4 | ||||||||||||||||||||||
| 2 | S Galdós S Martos Gornés | 4 | 4 | ||||||||||||||||||||||||
Sriram Balaji and Vishnu Vardhan were the defending champions but chose not to defend their title.
Omar Camporese and Goran Ivanišević were the defending champions but withdrew on the semifinals in order to focus on the singles tournament, in which both players reached the Final.
Damir Džumhur was the defending champion, but retired from his quarterfinal match against Jordan Thompson.
Pavel Kotov and Roman Safiullin were the defending champions but chose not to defend their title.
This was the first edition of the tournament.
This was the second of four editions of the tournament in the 2021 ATP Challenger Tour calendar.
Hunter Reese and Sem Verbeek were the defending champions but chose not to defend their title.
Sander Arends and David Pel were the defending champions but chose not to defend their title.
Filip Dewulf and Tom Vanhoudt were the defending champions, but Dewulf did not compete this year. Vanhoudt teamed up with Aleksandar Kitinov and lost in the first round to Emilio Benfele Álvarez and Hernán Gumy.
This was the first edition of the tournament.
Juan Garat and Roberto Saad were the defending champions, but Garat did not compete this year. Saad teamed up with Patricio Arnold and lost in the quarterfinals to David Adams and Andrei Olhovskiy.
Julian Lenz and Gerald Melzer were the defending champions but chose not to defend their title.
Carlos Taberner was the defending champion but was not eligible to compete in the tournament due to his ATP ranking.
Sergio Casal and Emilio Sánchez successfully defended their title by defeating Carl-Uwe Steeb and Michael Stich in the final, 5–7, 6–4, 6–3.
Evan King and Max Schnur were the defending champions but chose not to defend their title.
Sergio Casal and Emilio Sánchez were the defending champions, but lost to Omar Camporese and Goran Ivanisevic in the quarterfinals. Camporese and Ivanisevic went on to win the title, defeating Luke Jensen and Laurie Warder in the finals, 6–2, 6–3.
Diego Hidalgo and Cristian Rodríguez were the defending champions but lost in the semifinals to Jesper de Jong and Bart Stevens.
This was the first edition of the tournament.
Gonçalo Oliveira and Andrei Vasilevski were the defending champions but chose not to defend their title.
Nuno Borges and Francisco Cabral were the defending champions but chose not to defend their title.