2021 Open de Oeiras III – Doubles

Nuno Borges and Francisco Cabral were the defending champions but lost in the semifinals to Hunter Reese and Sem Verbeek.

Reese and Verbeek won the title after defeating Sadio Doumbia and Fabien Reboul 4–6, 6–4, [10–7] in the final.

Seeds
• # 🇵🇰 Aisam-ul-Haq Qureshi / 🇦🇺 Matt Reid (first round)

• # 🇻🇪 Luis David Martínez / 🇪🇸 David Vega Hernández (first round)

• # Romain Arneodo / 🇵🇱 Szymon Walków (quarterfinals)

• # 🇲🇽 Miguel Ángel Reyes-Varela / 🇧🇷 Fernando Romboli (first round)