Bell, who could only advance to the Championship 4 with a win Sunday, pit for new tires on the final caution and lined up sixth on the restart with 24 of 500 laps remaining.
He then methodically ran down and passed Chase Briscoe with four laps to go to reclaim the lead and held off Kyle Larson by 0.869 seconds for the win at Martinsville (Va.) Speedway.
The victory makes Bell one of the four drivers who will compete for the 2022 series title next weekend at Phoenix Raceway – his first such opportunity of his career.
“Mom and dad, we did it – wow!” Bell exclaimed after exiting his No. 20 Toyota. “I can’t believe it, man. To come here in Martinsville, this place has always been so tough on me. Just pre-race looking up, seeing all the fans, this place is packed.
“I don’t even know what to say. Just thank you so much to everyone on this Joe Gibbs Racing No. 20 team. They believed in me since day one.
“We went to Xfinity and did pretty well, struggled on the Cup side for the first little bit. They stayed with me. Very appreciative to be here. I don’t even know what to say.”
It was the second time in the playoffs Bell had produced a victory in a must-win situation. Needing a win to advance to the semifinal round, Bell came up with a win at the Charlotte Roval on Oct. 9.
Joining Bell with a chance to win the title at Phoenix are Joey Logano – who was already locked in by virtue of a win at Las Vegas, Chase Elliott and Ross Chastain, who used a desperation banzai move riding the Turns 3 and 4 walls wide-open to capture fifth.
Chastain went from 10th to fifth in the final corner and ended up claiming the last Championship 4 position by four points over Denny Hamlin, who finished sixth.
After the race, fourth-place finisher Keselowski was disqualified after the No. 6 failed to meet minimum weight requirements per NASCAR Rule Book Section 14.11.2. This will move everyone from Chastain on back up a position in the final finishing order.
Stage 3
Following the break between Stages 2 and 3, all the lead-lap cars pit with Hamlin first off pit road. On the restart on Lap 272, Hamlin was followed by Larson, Elliott, Ryan Blaney and Cole Custer.
NASCAR put out a caution on Lap 274 after Chastain washed up in the track and into Brad Keselowski, which sent Keselowski into the Turn 4 wall.
Logano, Keselowski and Chastain all pit under the caution. Logano said there was a small fire under the left-front of his No. 22 Ford.
Hamlin led the way on the restart on Lap 281 and was followed by Elliott, Larson, Custer and Blaney.
Austin Dillon wrecked in Turns 3 and 4 on Lap 320 which brought out the fourth caution of the race. It appeared Dillon’s No. 3 Chevrolet suffered a broken brake rotor.
The lead-lap cars all pit with Bell first off pit road. On the restart on Lap 330, Bell was followed by Blaney, Elliott, Hamlin and Larson.
With 150 laps remaining, Bell held almost a 1-second lead over Elliott as Blaney ran third and Hamlin fourth.
J.J. Yeley spun around off Turn 4 after contact from Corey LaJoie to bring out a caution on Lap 393. All the lead-lap cars pit with Bell first off pit road.
On the restart on Lap 404, Bell was followed Blaney, Elliott, Larson, Bubba Wallace and Hamlin.
With 57 laps to go, Bell made contact with Austin Cindric as he was attempting to put him another lap down which allowed Blaney to close the gap on the leader.
On Lap 467, Landon Cassill wrecked in Turn 3 and 4 to bring out the sixth caution of the race.
Most of the lead-lap cars pit but Briscoe stayed out and inherited the lead. Larson was first off pit road among those who pit.
When the race resumed on Lap 477, Briscoe was followed by Custer, Larson, Keselowski, William Byron (who took two tires), Bell, Blaney, Elliott, Logano, Wallace, Chastain and Hamlin.
With 10 laps to go, Keselowski moved into second behind Briscoe while Bell moved to third.
Stage 2
Hamlin cruised to the Stage 2 win by six seconds over Elliott with only 13 cars on the lead lap.
Larson was third, Custer was fourth and Bell rounded out the top-five.
Following the break between Stages 1 and 2, the lead-lap cars all pit with Hamlin first off pit road. Briscoe was penalized for removing equipment during his stop and had to restart from the rear of the field.
On the restart on Lap 140, Hamlin was followed by Elliott, Larson, Custer and Keselowski.
With 75 laps remaining in the stage, Hamlin held a small lead over Elliott as Larson ran third.
Tyler Reddick took his No. 8 Chevrolet to the garage on Lap 191 as he apparently was not feeling well. He was taken to the infield care center for evaluation after exiting his car.
With 50 laps to go, Hamlin had built his lead over Elliott to 2.2 seconds as Larson remained third, 4.7 seconds behind the leader.
With 20 laps remaining, Hamlin’s lead had expanded to more than 4.6 seconds over Elliott. Larson still ran third, 6.3 seconds behind the leader.
Stage 1
Hamlin, still looking to qualify for the Championship 4, held off Elliott to claim the Stage 1 win.
Custer was third, Larson fourth and Briscoe rounded out the top-five.
Larson started on the pole and quickly cleared Elliott for the lead.
After 40 laps, Larson got held up while trying to put Cassill a lap down which allowed Elliott and Blaney to close in right behind him.
With 75 laps remaining in the stage, Larson maintained about a half-second lead over Elliott as Briscoe made his way to third.
On Lap 69, Elliott gave Larson and shove, went to the inside off Turn 4 and grabbed the lead for the first time in the race.
Hamlin got around Larson to move into the second spot on Lap 96 as Custer took over third.
With 25 laps to go, Elliott held almost a 1-second lead over Hamlin as Custer ran third, 3.3 seconds behind.
On Lap 121, Hamlin finally ran down Elliot and passed him to the inside off Turn 4 to take the lead for the first time.
Kyle Busch, who fell three laps down, was warned by NASCAR to pick up the speed on his No. 18 Toyota.