Shawn Marion added 16 points for the Mavs, who secured the win only when Butler's potential go-ahead 3-point try was off-target in the final seconds.
The victory was the fourth straight for Dallas.
Butler, who played a key role in the Mavericks' NBA title run last season, was honored before the game when he accepted a championship ring. He left the squad as a free agent in December, signing a three-year, $24 million deal with the Clippers.
Butler ended with 23 points and eight rebounds while Blake Griffin contributed 20 and seven rebounds for Los Angeles.