One week after meeting with his coaches at UCLA and telling them he would remain in school, Adams informed them late Saturday night that he had changed his mind.
The 6-foot-5 Adams, who averaged 17.4 points per game last season, becomes the third member of the Bruins to declare for this year's draft, joining point guard Kyle Anderson and reserve guard Zach LaVine.
Alford said he was unsure why Adams changed his mind.
"I don't know why," Alford said in a text message to ESPN. "We lose four of five starters."
"Jordan informed us yesterday that he has decided to enter this year's NBA Draft, "Alford said in a statement. "He had two terrific seasons while at UCLA. I enjoyed coaching him this past season and wish him and his family all the best."
ESPN.com's Jeff Goodman and Andy Katz contributed to this report.