Morant drove forward, reached back with his right arm and launched a massive dunk with 4:20 remaining in the third quarter over Jalen Smith to open up a 20-point lead.
The Grizzlies guard finished the game with 23 points on seven-of-17 shooting from the field, with 10 assists and three rebounds.
Morant is averaging 28.7 points per game during the Grizzlies' nine-game win streak.
Desmond Bane was solid as always, going five-of-11 from three-point range in his team-high 25 points.
The victory means Memphis are tied with the Denver Nuggets at 29-13 for the best record in the Western Conference. The win was the Grizzlies' fourth straight on the road.
The Pacers, missing Tyrese Haliburton, were led by Chris Duarte with 25 points despite a hand concern.
Embiid seals Sixers victory over Jazz
Joel Embiid's jumper with 5.7 seconds remaining clinched a 118-117 victory for the Philadelphia 76ers over the Utah Jazz.
Embiid finished the game with 31 points on nine-of-18 shooting from the field with two three-pointers, seven rebounds and two blocks, while James Harden added 30 points and 11 assists.
Utah trailed for most of the game but hit the lead at 115-114 with 33 seconds left, with Jordan Clarkson scoring 38 points with nine rebounds.
Doncic kept to season low as Blazers fire
Doncic was benched with seven minutes to go by Mavs head coach Jason Kidd, in a game where the Blazers snapped a five-game losing run, having led 71-56 at half-time.
Lillard was exceptional with 36 points on 11-of-20 shooting with four three-pointers and 10 assists, while center Jusuf Nurkic added 22 points and 11 rebounds.