The players revealed their decisions individually on their social media accounts.
Akinjo still had another season of eligibility at Baylor, where he transferred last year after leading Arizona in scoring in his only season with the Wildcats. He began his college career at Georgetown.
Brown, a five-star recruit whose dad is a former Harlem Globetrotters player, averaged 9.7 points and 4.9 rebounds a game while starting all 34 games for the Bears. He is projected to be the No. 25 pick in ESPN's latest mock draft.
"I feel so fortunate for all that I've experienced this season at Baylor University! We accomplished so much as a team and grew together," Brown said in part in a statement posted on his Twitter account.
Akinjo ranked ninth in the Big 12 averaging 13.5 points a game, and led the conference with 5.8 assists per game.
In an Instagram post, Akinjo said he had decided to pursue his dream and enter the NBA draft after talking it over with his family. He said he planned to hire an agent.
"Thank you to the Baylor coaching staff for welcoming me into the program, to my teammates for helping me get better every day," part of Akinjo's post read.
Brown and Akinjo became starters after joining a Baylor team that was coming off a national championship last season.
The Bears were the No. 1 seed in the East Region this season and lost in overtime in the second round of the NCAA tournament to Final Four team North Carolina. Baylor overcame a 25-point deficit in the second half and tied the score on Akinjo's second three-point play in the final 1:48 of regulation.
The Associated Press contributed to this report.