The deal would include a player option for the 2014-15 season and is set to be finalized sometime this week. The Clippers have already added J.J. Redick and Jared Dudley this offseason as well as re-signed point guard Chris Paul.
The Los Angeles Lakers were one of several teams to pursue Mullens.
Mullens, who can play the 4 or 5 position, spent the last two seasons with Charlotte Bobcats and averaged 10.4 points and 6.4 rebounds in 2012-13.
THOMSEN: Busy offseason shows these are not the Clippers of yore Mullens was a first-round pick in the 2009 draft and in four NBA seasons, including two with the Oklahoma City Thunder, he has averaged 8.4 points and 4.8 rebounds a game.