Rebels coach Dave Rice made the announcement Friday, saying the junior had provided great energy and leadership while with the team.
Smith averaged 10.9 rebounds per game during the 2013-14 season and 11.1 points. He had 16 double-doubles last season.
In a statement issued by the school, Smith said he had a great experience at UNLV and plans to finish his classes while preparing for the draft.
Smith originally came to UNLV as a transfer from Connecticut, where he was a member of the Huskies' 2011 NCAA championship team.