Topping East Group A with four wins from four during the group stage, Rick Carlisle's Pacers had it all to do in the second half of their clash with the Celtics, who led 55-48 at the midway mark.
However, the Indiana outfit sparked a phenomenal turnaround in the third and fourth quarters thanks to an inspired display from Tyrese Haliburton, who registered the first triple-double of his career.
The 23-year-old was forced to sit out the weekend's success over the Miami Heat due to illness, but he ended the contest with 26 points, 10 rebounds and 13 assists to his name as the Pacers caused a major upset.
Buddy Hield also registered 21 points for the victors, while Jayson Tatum led the way for the Celtics with 32 points and 12 rebounds, alongside 30 points for Jaylen Brown, but their efforts were in vain.
The Pacers will now battle for a spot in the final against either the Milwaukee Bucks or New York Knicks, where they could find themselves pitting their wits against the Pelicans thanks to their successful exploits at Golden 1 Center.
The Kings came into the knockout stage with a perfect 4-0 to boast from their West Group, in comparison to the Pelicans' record of three victories and one defeat, but the New Orleans franchise had the psychological edge with two wins over their hosts already this season.
Willie Green's men had a one-point disadvantage to make up after the first quarter and did so with aplomb, as Brandon Ingram amassed 30 points while Jonas Valanciunas achieved a double-double, posting 18 points and 11 rebounds.
Speaking to the press after the match, as quoted by ESPN, Green placed particular emphasis on the "trust" he witnessed between his group of players, saying: "The biggest thing I saw in that game was trust.
"Our guys just stuck together, they stuck together in the huddle, and they continued to make the right play over, and over and over again. When you see a team that has 29 assists and only 14 turnovers, that's a team that's continuing to trust. We want to continue to build on that."
The Pelicans will take on the Los Angeles Lakers or Phoenix Suns in the final four, although their triumph was overshadowed by the death of a fan who suffered a medical emergency during the match.