Kevin Durant notched a double-double of 19 points and 10 rebounds for the Thunder, who scored 25 points off the fast break to help shake off a recent spell of up-and-down play.
The victory was only the fourth in eight games for Northwest Division-leading Oklahoma City.
The Mavericks, meanwhile, made only 3-of-16 three-point attempts in losing for the fifth time in eight outings.
Shawn Marion led Dallas with 23 points.
Notable deaths of 2014 [PHOTOS]
Michael Sam cut from the Dallas Cowboys