Lee, 6-foot-5, had previously announced he was only testing the waters of the NBA draft without an agent, thus preserving his NCAA eligibility, but he said Tuesday that he changed his mind.
"After speaking to my family, I have carefully weighed all of my options, and at this time, I have decided to hire an agent and withdraw from my classes," Lee said in a statement. "My dream has always been to play in the NBA and I think that this is the best time for me to try and make that a reality."
Lee averaged 13.1 points for the Bruins last season and is considered one of the top perimeter defenders in the nation. He earned All Pac-10 and Pac-10 All-defensive team honors, but is thought by many to be a year away from being NBA ready.
An NBA front office source, speaking on condition of anonymity, said Lee would go in the second round at best and could go undrafted. ESPN.com's Chad Ford has him ranked as the No. 73 prospect in the country.
However, Howland said his NBA front-office sources have indicated that Lee would go in the second round, which carries some risk because second-round picks don't figure as prominently as first-round picks in the plans of the drafting team.
"So his thing right now is to try to do a great job in his preparation so that he can try to get himself ready and try to get himself into the first round," Howland said.
Complicating matters is the surgery Lee had to repair a torn meniscus in his left knee on March 22. Lee is still rehabilitating the injury and Howland said he is still at least three weeks away from being able to play at pre-surgery levels.
Howland said he advised Lee to come back to school to try and improve his draft status and spoke with Lee's family, but ultimately Lee had the final say.
"In my opinion, I thought that would have been in his best interest," Howland said. "Obviously that is what's best for UCLA basketball, but I honestly, in my heart, really believed that with all the factors that was in his best interest."
Lee's departure is the second this offseason for the Bruins, following Tyler Honeycutt's exit on March 29. The Bruins had been projected as a preseason top-10 team next season, but the losses of Lee and Honeycutt tempers expectations.
"I really believe that if we had both of them back we would have had a chance to challenge, no question, in that category," Howland said.
Howland said Lee plans to move to Las Vegas and begin his pre-draft workouts as he rehabs his knee.
Still, Howland has reason for optimism. Twins David Wear and Travis Wear, 6-foot-10 transfers from North Carolina, will be eligible, and incoming freshman guard Norman Powell will help fill the void left by Lee. Also, Howland said he would announce another signing -- expected to be City College of San Francisco transfer De'End Parker, another 6-foot-5, athletic guard.
Forward Reeves Nelson, the team's leading scorer and rebounder, will be back, as will 6-foot-10, 305-pound center Joshua Smith, who is primed to become the top big man in the country as a sophomore next season.
"I'm very, very optimistic and excited about our team next year," Howland said. "We're going to be very young. We're going to have a very formidable front line."
Peter Yoon covers UCLA for ESPNLosAngeles.com. Information from The Associated Press was used in this report.