The Clippers received a conditional future second-round pick in return.
Matt Barnes, who had been reportedly part of the Clippers' trade talks, said it was tough to lose any teammates.
"I'm just relieved that it's over and now our only focus is winning games with the group we have," Barnes said. "We know we have enough of what it takes to win it."
The 7-foot Mullens has averaged just 2.5 points and 1.2 rebounds in 27 games this season with the Clippers.
Mullens, 25, averaged career highs in points (10.6) and rebounds (6.4) last season with the Charlotte Bobcats.
Mullens was the 24th overall pick in the 2009 draft by the Dallas Mavericks. He is in his fifth season.
Information from ESPNLosAngeles.com's Arash Markazi was used in this report.