Doncic rattled off his eighth straight 30-point game to finish with 33 points, 17 assists and six rebounds in a thrilling back-and-forth duel with the Lakers, who were playing their first game since winning the inaugural in-season tournament on Saturday.
An absorbing contest at Dallas's American Airlines Center home saw the lead change hands eight times, with the Lakers overturning a 15-point deficit with a huge third quarter to help open up a four-point lead early in the fourth.
But Dallas's Dante Exum took over with a superb display in the final period that saw him rattle in 17 points -- including five three-pointers -- to carry the Mavs to victory.
Exum finished with 26 points while Tim Hardaway Jr. added 32 points from the bench to support Doncic.
Anthony Davis led the Lakers scoring with 37 points from 15-of-21 shooting, with James adding 33.
Doncic stayed in the game despite rolling an ankle and suffering a bloodied lip in a physical battle between the two Western Conference rivals.
"I'm not going out in a game like this, no way," the Slovenian star said. "When you're playing against the best you want to stay on the court.
"This was an amazing team win. We've got so many guys out, everybody stepped up, everybody played hard."
Green, Jokic tossed
Doncic admitted he was flattered by talk of him potentially emerging as a contender for the NBA's Most Valuable Player award -- but insisted team success was more important than individual honors.
"Of course, who wouldn't want to be MVP of the league?" Doncic said. "But obviously first is the championship... that's what's first on my mind for sure."
The win saw the Mavericks improve to 15-8 for the season while the Lakers fell to 14-10 to remain sixth in the West.
In other games, Draymond Green could be facing more disciplinary action from the NBA after being ejected for the third time this season in the Golden State Warriors' 119-116 defeat to the Phoenix Suns.
Green, suspended for five games last month after grabbing Minnesota's Rudy Gobert in a choke hold, was tossed once again in the third quarter after wildly swinging an arm into the face of Phoenix player Jusuf Nurkic.
The game eventually ended in victory for the Suns, with Devin Booker scoring 32 points as the Warriors slid to a sixth straight defeat on the road.
There was also a high-profile ejection in Chicago, where Denver star Nikola Jokic was controversially tossed from the game in the second quarter of the Nuggets' 114-106 defeat of the Chicago Bulls.
Jokic was ejected after reacting angrily to a no-call with a member of the officiating crew.
In Boston, the Celtics recovered from a shaky start to beat the Cleveland Cavaliers 120-113 and preserve their unbeaten home record.
Jayson Tatum and Jaylen Brown scored 25 points apiece while Kristaps Porzingis finished with 17 on a night when all five starters posted double-digit tallies.
But the Eastern Conference leaders were made to work hard for the win after trailing by 15 points in the first quarter following a slew of turnovers and some woeful shooting.
The Cavs led by 10 after the first period but the Celtics responded with a 38-point second period to cut the gap to one point at half-time.
In a game that had nine lead changes, the Celtics finally edged clear midway through the fourth quarter to close out victory.
Donovan Mitchell led the Cleveland scoring with 29 points with Darius Garland finishing with 26.
"We got off to a slow start but we picked it up and some shots started to fall," Tatum said.
