Gonzaga's leading scorer and the West Coast Conference player of the year, Petrusev made his announcement Sunday, the deadline for players to declare.
Petrusev also submitted his name for the draft after his freshman season, when he played limited minutes.
"It is my dream to one day play at the highest level so I am entering the 2020 NBA draft, but I am still considering a return to Gonzaga," Petrusev said in a news release. "There is still a lot of uncertainty with what might happen to next year's NCAA season as well as the NBA draft, this gives me more time to evaluate that and leave all the options open.
Petrusev, a 6-foot-11, 235-pound native of Serbia, led the Bulldogs in scoring (17.5 points per game) and rebounding (7.9 per game) last season as a sophomore. The Zags finished 31-2.