The 1990 Yugoslav Open was a men's tennis tournament played on outdoor clay courts in Umag, Yugoslavia that was part of the World Series (Designated Week) of the 1990 ATP Tour. It was the first edition of the tournament and was held from 14 May until 20 May 1990. No.1 seed Goran Prpić won the singles title.[3]
| 1990 Yugoslav Open | |
|---|---|
| Date | 14–20 May |
| Edition | 1st |
| Category | World Series |
| Draw | 32S / 16D |
| Prize money | $175,000 |
| Surface | Clay / outdoor |
| Location | Umag, Yugoslavia (current Croatia) |
| Champions | |
| Singles | |
 Goran Prpić[1] | |
| Doubles | |
 Vojtěch Flégl / Daniel Vacek[2] | |
Finals
Singles
Goran Prpić defeated Goran Ivanišević, 6–3, 4–6, 6-4
- It was Prpić's only ATP singles title of his career.
Doubles
Vojtěch Flégl / Daniel Vacek defeated 
Andrei Cherkasov / Andrei Olhovskiy, 6–4, 6–4
- It was Flégl's first doubles title of his career. It was Vacek's first doubles title of his career.