The miscue occurred with about 7:50 remaining in the frame. The Warriors led 66-61. Kevin Durant threw a pass to Stephen Curry on the play. Curry then dished out to Draymond Green at the 3-point line. Curry ran out to the 3-point line and got the pass back, but was picked up by two Cavaliers defenders.
The Warriors star passed to McGee, who was wide open under the hoop. The 7-foot, 270-pound center caught the pass and took one dribble, while his back was to the rim. He then turned his body and jumped up, but he drilled the underside of the rim with a two-handed dunk attempt.
McGee turned the ball over and put the Cavaliers in transition. The Cavaliers bench enjoyed the miscue, as several players could be seen laughing at McGee's error.
McGee scored four points and had a rebound and a block in the Warriors' 124-114 victory.
"Good Win fellas ... not even gone lie even I laughed at that one! Three more," McGee tweeted.
The Warriors and Cavaliers resume the NBA Finals at 8 p.m. Sunday at Oracle Arena in Oakland.