2021 Zagreb Open – Singles

This was the first edition of the tournament since 2011.

Sebastián Báez won the title after defeating Juan Pablo Varillas 3–6, 6–3, 6–1 in the final.

Seeds
• # 🇦🇷 Federico Coria (second round)

• # 🇪🇸 Pedro Martínez (quarterfinals)

• # 🇸🇰 Andrej Martin (second round)

• # 🇯🇵 Yasutaka Uchiyama (first round)

• # Pedro Sousa (first round)

• # 🇫🇷 Benjamin Bonzi (first round)

• # 🇧🇦 Damir Džumhur (second round)

• # 🇧🇷 Thiago Seyboth Wild (quarterfinals)