Marc Jackson added 19 points for the Hornets, who rallied from a seven-point fourth-quarter deficit and a three-point overtime deficit.
Mason's basket from underneath the goal with 25.3 seconds left in overtime put New Orleans ahead 98-97. Memphis' Chucky Atkins threw the ball away with 8.3 seconds left, and Jannero Pargo hit two free throws with 6.6 seconds left to give the Hornets a three-point lead.
Damon Stoudamire missed a well-guarded 3-point attempt at the buzzer for the Grizzlies. Pau Gasol led Memphis with 28 points, but played only 2 minutes in overtime and wasn't in the game in the final minute.
Box score and recap here.