The Timberwolves held a two-point lead with 11 seconds remaining when Doncic took possession up against defensive player of the year Rudy Gobert.
Facing up the 7ft 1in Frenchman, Doncic created space off the dribble before slotting a step-back three-pointer.
Asked about the match-up in his side’s final attacking play, Doncic said: “I can’t move fast, but I can move faster than him.”
The Timberwolves had one final chance to win the game when they found Naz Reid in a shooting position but he missed the basket.
Reid top-scored for his side with 23 points but Anthony Edwards and Karl-Anthony Towns struggled again – combining for just 36 points.
Games three and four are at the Mavericks’ American Airlines Center on Monday and Wednesday.
Elsewhere, the Boston Celtics are 2-0 up against the Indiana Pacers in the Eastern Conference Finals.
The winners of the two series will meet in the NBA Finals – and game one will be broadcast live on BBC One from 01:30 BST on Wednesday, 7 June.
