Trading baskets in the first quarter, the Kings were able to separate themselves from the Mavs by as much as 11 points, leading 49-42 at the half.
The Kings blew the door wide open with a 7-0 run to start the second half and their lead grew to 17 points in the third quarter, but a veteran Dallas team wouldn't go down quietly.
The Mavs did most of their damage with the Kings' bench on the floor and eventually took a five-point lead. With time running out in the game, Isaiah Thomas hit a three-pointer off the glass to send the game into overtime.
With the Kings down 111-109, Cousins fouled out after turning the ball over. His personal foul was upgraded to a flagrant foul two, an automatic ejection after hitting Vince Carter in the head.
The ejection was too much for the Kings to handle as they lost 117-112.
Cousins finished with 29 points on 9-of-14 shooting, nine rebounds and four assists and Tyreke Evans had 20 points, seven rebounds and three blocks.
Playing a little over seven minutes, Marcus Thornton went scoreless in his return to the court for the first time since spraining his left ankle against Boston on Dec. 30.
O.J. Mayo scored 24 points and 10 rebounds for the Mavericks, Carter added 23 points and Shawn Marion finished with 19 points and 10 rebounds.
Kings coach Keith Smart said that turning the ball over 20 times, leading to 23 points for Dallas, was a big reason why his team came up short:
"I thought these guys did a great job here tonight. ... The game, it was kind of in (Dallas') favor with some veteran guys that have some know-how to be able to close the game and make some plays."
The Kings will host the defending champion Miami Heat on Saturday at 7 p.m. PST.