Okpala, a first-team all-Pac-12 honoree this season, is ranked No. 26 on ESPN's list of the top 100 draft prospects.
"The NBA is a dream and certainly a goal of mine," Okpala said in a statement. "I am truly blessed to continue to learn from so many people here at Stanford as I grow as a person and a player. It's exciting to apply what I have learned so far as I begin this journey and see where it takes me."
Okpala led Stanford in scoring last season at 16.8 points per game while also contributing 5.7 rebounds and 2.0 assists per contest.
Under NCAA rules, Okpala has until May 29 to decide to remain in the draft or return to the Cardinal.