Reddick got through Turn 1 on the restart unscathed while most of the field did not, including Ross Chastain, who ran off onto the access road and returned to the track in the lead.
With multiple cars going off track battling for position, Reddick eventually ran Chastain down and passed him for the lead and held on for the victory.
Chastain, however, was penalized by NASCAR for cutting the corner and dropped to 27th place.
The win is the second of Reddick’s career with both coming this season and both on road courses.
“I was like, ‘uh-oh’. But that was a scenario that had been talked about,” Reddick said of Chastain’s move. “If you get bottled up, what do you do? Take the access road.
“I couldn’t believe he got ahead of me. I was kind of waiting to see if he was going to have a penalty because I didn’t want to move him out of the way and make his race worse than what it was.
“Yeah, I was really surprised by that, but hey, we made it work. Hats off to Ross for trying to do that, but really glad it didn’t end up working out because I’d have been pretty (upset).”
Sunday’s win comes after Reddick announced a couple weeks ago that he would be leave Richard Childress Racing after the 2023 season and to join 23XI Racing.
Asked how his team has been able to remain focused on winning, Reddick said, “We just know what we’re capable of, and we did that at Road America. Certainly it was a little bump in the road, but we went out and won a race fair and square a couple weeks ago and if we change nothing, we keep working really, really hard, we find a way back to Victory Lane.
“Just really glad to be able to do it here in Indianapolis. This is one really special place to race, and really excited to kiss the bricks.”
With the revised results, Austin Cindric was credited with second, Harrison Burton a career-best third, Todd Gilliland fourth and Bubba Wallace fifth.
Completing the top-10 were Joey Logano, A.J. Allmendinger, Michael McDowell, Cole Custer and Chris Buescher, who at one point was two laps down early in the race.
Stage 3
During the break between Stages 2 and 3, several cars pit but Christopher Bell was among those who stayed out and remained in the lead.
On the restart on Lap 40, Bell was followed by Wallace, Ty Dillon and Denny Hamlin and Chase Briscoe. Reddick lined up eighth.
Brad Keselowski went for spin in Turn 7 on Lap 41 but returned to the track without an issue.
Reddick moved into second on Lap 43, 3.3 seconds behind Bell.
Ty Dillon was the first of the lead-lap cars to make his final green-flag stop on Lap 49 for new tires and fuel to make it to the end of the race. Wallace, Briscoe and Hamlin followed on Lap 50.
On Lap 51, Reddick finally got around Bell to retake the lead. On Lap 52, Reddick decided to make his final stop which turned the lead over to Ryan Blaney.
On Lap 57, Allmendinger, Suarez and Cindric all pit.
On Lap 61, Kyle Larson went into Turn 1 and lost his brakes and viciously slammed into Ty Dillon’s No. 42 to bring out the caution.
A handful of drivers pit but most stayed out and Reddick remained in the lead. On the restart on Lap 65, Reddick was followed by Bell, Blaney, William Byron and Allmendinger.
Kevin Harvick and Alex Bowman crashed on Lap 66 and several went off course. All made it back on the track without need of a caution but Harvick was forced to pit.
With 10 laps to go, Reddick’s lead over Blaney improved to 2.9 seconds as Chase Elliott ran third, 3.3 seconds behind the leader.
Elliott got around Blaney for second with nine laps to go.
On Lap 77, a large piece of the right-front fender off Bell’s No. 20 Toyota landed on the frontstretch and forced NASCAR to display the caution.
A handful of cars pit but Reddick remained on the track and in the lead when the race resumed with three laps to go. He was followed by Elliott, Blaney and Allmendinger.
After Reddick cleared for the lead in Turn 1, chaos erupted behind him as the field went five-wide sending multiple cars spinning and off the track.
Austin Dillon ended up stuck in the gravel which is what brought out the caution and sent the race into overtime. Reddick led the way on the restart followed by Allmendinger, Blaney, Chastain and Suarez.
Stage 2
Bell easily held off Kyle Busch to take the Stage 2 win as most of the lead-lap cars pit before the stage break.
Wallace was third, Elliott fourth and Ty Dillon rounded out the top-five.
During the break between Stages 1 and 2, several lead-lap cars pit but Blaney was among those who stayed out and inherited the lead.
On the restart on Lap 20, Blaney was followed by Byron, Keselowski, Corey LaJoie and Reddick.
Both Harvick and Elliott went off course entering Turn 1 as Blaney cleared for the lead.
Alex Bowman was forced to pit under green on Lap 21 for a flat tire which he picked up in an incident with Harvick and Ty Gibbs.
On Lap 25, both Aric Almirola and Larson both fell off the pace with flat tires after making contact and were forced to pit under green.
With 10 laps left in the stage, Blaney continued to fend off a hard challenge for the lead by Byron as Reddick had moved up to third.
On Lap 27, Allmendinger went off and into the gravel in Turn 6. He was able to return to the course.
With five laps remaining, several drivers began hitting pit road for green-flag pit stops. Blaney continued to lead with Reddick having moved up to second.
On Lap 32, Daniil Kvyat came to stop off track after he lost power in his No. 26 Ford. The former Formula 1 driver was making his Cup series debut.
Several more lead-lap cars elected to pit before the stage break but Bell stayed out and inherited the lead on Lap 33.
Stage 1
Several lead-lap cars pit before the stage break, but Chase Briscoe remained on the track and easily held of Blaney to take the Stage 1 win.
Byron was third, Logano fourth and Elliott rounded out the top-five.
Reddick started on the pole and cleared for the lead in Turn 1 as Justin Haley spun off the track. He was able to continue without a caution.
On Lap 2, Hamlin spun in Turn 6 but was able to return to the course and continue on.
After five laps, Reddick moved out to a 2.3-second lead over Cindric while Briscoe ran third. Hamlin missed Turn 1 and dropped to 34th in the running order.
On Lap 7, Keselowski spun and missed Turn 1 but quickly returned to the course.
With five laps remaining in the stage, Reddick maintained a 1.9-second lead over Cindric as Briscoe remained in third.
Several cars, including Reddick, elected to pit before the end of the stage break. Buescher also pit and had to have a small fire put out under his No. 17 Ford and fell two laps down after repairs.
Briscoe stayed out and inherited the lead on Lap 13.
Cody Ware (unapproved adjustments) and Almirola (engine change) had to start the race from the rear of the field.