Cleveland's all-star point guard hit a three with 0.9 seconds left as part of a 32-point performance, and the Cavaliers edged the Raptors 99-98 on Saturday.
"Kyrie threw up a bomb, he made a hell of a shot," Toronto's Amir Johnson said.
With the clock ticking down and the Raptors thinking overtime at worst, Irving — named an Eastern Conference reserve for next month's all-star game — calmly walked up the court and chucked up a 30-foot shot over Alan Anderson.
"(Anderson) was at the three-point line. I (he paused to chuckle) was a little bit further back," irving said.
Johnson topped Toronto (16-28) with 18 points and 12 rebounds, while Anderson added 17 points, Ed Davis finished with 16, DeMar DeRozan scored 15 and Jose Calderon added 10.
Marreese Speights finished with 17 for the Cavs (13-32), who've won three in a row.
Tristan Thompson of Brampton, Ont., the highest Canadian ever taken in the NBA draft — No. 4 in 2011 — had 14 points and eight rebounds in 33 minutes for Cleveland.
"Mom's not going to spank me tonight," Thompson joked about getting a win in his hometown.
The Raptors — dressed in their camo uniforms in honour of the Canadian Forces — led almost the entire game and took a nine-point advantage into the fourth quarter.
But the Cavs raced out on a 12-0 run early in the final quarter, eliciting groans from the Air Canada Centre crowd of 18,820 fans that have seen too many late-game collapses from Toronto of late.
"I think we played well enough to win this game, it's a tough one," Calderon said. "(Irving) made a great three. . . but still, we shouldn't have got in that situation."
Irving's jumper with 3:38 to go put the Cavs up by five — Cleveland's biggest lead of the game. Raptors rookie Terrence Ross was big down the stretch, draining a pair of threes, and a layup with 2:11 that tied the game at 94-94.
A Ross rebound led to a dunk by Johnson that gave the Raptors the lead with 1:16 to play. Irving and Calderon traded layups, Calderon's putting Toronto up by two with 13 seconds left and delighting the fans that cheered at ear-splitting levels.
Irving's three instantly silenced them.
"He pretty much facilitated the game," Johnson said of Irving. "He was driving, we did our best to double-team him, he just made some really tough shots. We gave him one at the end. . . I don't even know how many feet that was away from the three-point line."
A loss to a team below them in the standings was a big blow to a Raptors team that began the night four games back of Boston for the eighth and final playoff spot in the Eastern Conference, and four-and-a-half games ahead of the Cavs.
The short-handed Raptors should get some help within the next couple of weeks. Raptors coach Dwane Casey said Andrea Bargnani and Jonas Valanciunas could return to the lineup within about a week and a half. Bargnani (torn elbow ligament) has missed 22 games, while Valanciunas (broken finger) has missed 16.
"The thing is incorporating them back in to how we want to play, and how we're playing now," Casey said.
DeRozan scored 12 points in a first quarter that saw the Raptors shoot 58 per cent. Toronto was ahead by as much as 10 before taking a 25-19 lead into the second.
The Raptors went up by 11 on an Anderson jumper early in the second, but the Cavs chipped at the lead to pull within two with about 30 seconds left in the half. A Davis dunk sent the Raptors into the dressing room with a 50-46 lead.
The visitors made it a two-point game several times in the third but the Raptors outscored Cleveland 25-20 in the quarter to lead 75-66 with one quarter left.
NOTES: Former Raptor Jorge Garbajosa was at the game, and received a warm ovation when he was shown on the Jumbotron. . . The Raptors host Golden State on Monday then travel to Atlanta on Wednesday. They host the Los Angeles Clippers on Friday to begin a tough three-game homestand that also includes visits by the Miami Heat and Boston Celtics. . . The Raptors had won six of their previous matchups with Cleveland.