Ellis also had nine assists, and Larry Sanders notched a double-double with 13 points and an equal number of rebounds.
Milwaukee chalked up a needed victory after dropping seven of their previous eight games.
Dirk Nowitzki led Dallas with 21 points and 20 rebounds. The Mavericks out-rebounded the Bucks 56-39 but went 1-for-17 from 3-point range and lost their second consecutive contest.
Dallas tied the score at 90-90 with 1:21 to play on a layup by Elton Brand but the Bucks scored the final five points of the game to hang on for the win.
Notable deaths of 2014 [PHOTOS]
LeBron James reveals his new Nike shoes