Derrick Favors registered 13 points and eight rebounds as the Jazz won the series four games to two. Rudy Gobert contributed 12 points and 13 rebounds, Joe Ingles also scored 12 points and Alec Burks added 11.
The fifth-seeded Jazz will face the top-seeded Houston Rockets in the second round, with the series starting Sunday.
Russell Westbrook made seven 3-pointers while recording 46 points and 10 rebounds for the fourth-seeded Thunder. It was Westbrook's seventh career postseason 40-point outing.
Steven Adams had 19 points and 16 rebounds for Oklahoma City while both Carmelo Anthony (seven points on 3-of-7 shooting) and Paul George (five on 2-of-16 shooting) had subpar outings.
Mitchell has scored 171 points, third most through six games by a rookie in NBA history. Lew Alcindor, who later changed his name to Kareem Abdul-Jabbar, had 216 in 1970 and Wilt Chamberlain scored 199 in 1960.
Mitchell was glad to be celebrating a close-out win after Utah blew a 25-point lead and lost Game 5.
"We worked hard, we stuck with it," Mitchell said during a postgame television interview on ESPN. "After Game 5, there was some question if we could handle it but the character of this team is just incredible. We all did what we were supposed to do, and we all came up big."
Utah played most of the contest without point guard Ricky Rubio, who exited with a left hamstring injury with 4:52 remaining in the first quarter.
Westbrook drained a 3-pointer to cap a 10-2 surge and pull the Thunder within 92-91 with 1:28 remaining. Favors hit a jumper 20 seconds later to give the Jazz a three-point lead before Oklahoma City missed its next six shots -- the last in the sequence being an airball 3-pointer by George while seemingly being bumped after a pump fake -- before Mitchell made two free throws with 6.9 seconds left to seal it.
The score was tied at the break before Mitchell exploded in the third quarter with 22 points on 8-of-10 shooting as Utah nearly matched its first-half output (41 points) with a 37-point quarter.
"I was surprised by the third quarter because to say that I expected all this, I'd be lying to you," Mitchell said afterward, per ESPN. "But this feels incredible, man."
Mitchell scored 15 points over the first 5:27 of the period with his third 3-pointer of the quarter giving the Jazz a 62-52 lead. Mitchell improved to 8-of-8 shooting in the quarter when he converted a three-point play to make it 73-61 with 3:22 left.
Westbrook kept the Thunder in the game by scoring 20 points in the quarter and Oklahoma City trailed 78-70 entering the final 12 minutes.
Westbrook drained a 3-pointer to open the fourth quarter but Utah answered with eight straight to take an 86-73 lead with 7:04 to play. He then scored five points during an 8-0 run as the Thunder crept within five with 5:31 left.
Westbrook had 15 first-half points in a game that was knotted at 41 at halftime.
--Field Level Media
Oklahoma City | Utah | |
Russell Westbrook 46 | Scoring | Donovan Mitchell 38 |
Paul George 8 | Assists | Joe Ingles 5 |
Steven Adams 16 | Rebounds | Rudy Gobert 13 |
Russell Westbrook 3 | Free Throws Made | Donovan Mitchell 5 |
Russell Westbrook 2 | Steals | Rudy Gobert 2 |
Alex Abrines 1 | Blocks | Rudy Gobert 3 |
Team | Points | FG% | 3PM-3PA | FTM-FTA | Assists | Rebounds | Blocks | Steals | Turnovers |
Oklahoma City | 91 | 39.8 | 10-34 | 7-13 | 20 | 49 | 4 | 6 | 13 |
Utah | 96 | 45.1 | 10-26 | 12-23 | 16 | 40 | 5 | 9 | 13 |