The Kings ended their longest losing streak of the season at six games and won on the road for just the fourth time this season. Sacramento finished a six-game journey at 1-5 and will play 11 of its next 14 contests at home.
Washington had a nine-point lead in the third period but fell behind for good with 4:57 remaining in the game.
The Wizards trailed by only three when Thornton began a 6-0 run with his tip-in. Isaiah Thomas then made a layup and Chuck Hayes hit two foul shots to put Sacramento ahead 112-103 advantage with 1:49 to go.
Thornton and Tyreke Evans both had 22 points for the Kings. Thomas added 16 points and 16 rebounds.
Washington, which has lost four straight, got 32 points from Jordan Crawford.
Dennis Rodman pledges to end trips to North Korea
Jessica Simpson shares three-way kiss with friends in photo