Nemechek, who joined Kyle Busch Motorsports in the offseason, got a push from Busch on a restart with six of 134 laps remaining to shoot him past Austin Hill.
Nemechek, 23, then held off his boss to win Friday night’s Bucked Up 200 at Las Vegas Motor Speedway. The win is Nemechek’s first of the season and first NASCAR national series win since 2018.
While Nemechek is competing fulltime in the No. 4 Toyota, Friday was Busch’s first series race of the 2021 season.
“I just can’t thank everyone at Toyota, Kyle Busch, just everyone for this opportunity – it means the world to me,” Nemechek said. “Coming back to the Truck Series, that was plan; that was the goal – we’re here for wins.
“I think my experience paid off tonight. This team did an amazing job. Thank the fans for being here. It’s awesome and I can’t wait to celebrate.”
Asked what Nemechek thought would develop with Busch pushing him on the last restart, he said, “He was faster than me in Stage 2. I really didn’t know. It was an awesome victory.”
Austin Hill ended up third, Stewart Friesen was fourth and Matt Crafton rounded out the top-five.
Rounding out the top-10 were Zane Smith, Grant Enfinger, Parker Kligerman, Christian Eckes and Ben Rhodes.
Following the break between Stages 2 and 3, all lead-lap trucks pit with Friesen the first off pit road.
On the restart on Lap 68, Friesen was followed by Nemechek, Busch, Crafton and Austin Hill.
Busch shoved Nemechek back into the lead after the restart.
On Lap 69, Conor Daly wrecked hard into the Turn 1 wall in an incident that also involved Tyler Hill.
“It was less than comfortable,” Daly said of his wreck. “I was having so much fun. This truck was awesome. I just got in the middle of 3-wide … or 4 or 7 … and the air just swooped me around. That’s just inexperience.
“It felt like someone hit my right rear and pushed me around.”
The race returned to green on Lap 76 with Nemechek out front, followed by Busch and Austin Hill.
On Lap 79, Chandler Smith spun off Turn 2 and appeared to get some help from Dawson Cram. Several trucks elected to pit during the caution but Nemechek remained on the track and in the lead on the restart on Lap 84.
Busch fell off the pace and on Lap 89 spun off Turn 2 with a flat tire to bring out a caution. Most of the lead-lap trucks pit with Peters the first off pit road thanks to a two-tire stop.
Brett Moffitt stayed on the track and inherited the lead. He led the way on the restart on Lap 96 followed by Todd Gilliland, Rhodes, Kligerman, Tanner Gray and Timothy Peters. Nemechek lined up seventh.
Raphael Lessard came down on David Gilliland in Turn 1 on Lap 97 to ignite a multi-truck wreck that also collected Hailie Deegan, Bret Holmes and Ryan Truex.
Moffitt remained in the lead when the race returned to green on Lap 104 followed by Nemechek and Kligerman. Busch returned to the lead lap and restarted 24th.
Using a three-wide move on the restart, Nemechek powered back into the lead as Moffitt fell back to second.
On Lap 115, Roper wrecked again on the frontstretch, collecting Tyler Hill and bringing out another caution.
Nemechek continued to lead on the restart on Lap 122. He was followed by Austin Hill, Rhodes, Crafton and Friesen. Busch lined up ninth. Kligerman had saved a set of tires, pit to put them on and lined up 17th.
Tyler Ankrum and Jordan Anderson wrecked on the backstretch after some contact with Chase Purdy on Lap 123, forcing another caution to come out.
Nemechek remained the leader when the race returned to green with six laps remaining. He was followed by Austin Hill and Busch.
With five laps to go, Busch got behind Nemechek in an attempt to run him down for the lead and the win.
Once Busch got out front, he had little trouble staying there and easily held off Nemechek to take the Stage 2 win, his first stage victory of the 2021 season.
Friesen was third, Crafton fourth and Rhodes rounded out the top-five.
Following the break between Stages 1 and 2, all the lead-lap trucks pit with Nemechek the first off pit road.
On the restart on Lap 37, Nemechek was followed by Sheldon Creed, Busch and Friesen.
On Lap 48, Busch got around Nemechek to take the lead for the first time. Friesen ran third, Crafton fourth and Rhodes rounded out the top-five.
With five laps remaining in the second stage, Busch had opened up a more than 1.5-second lead over Nemechek.
Nemechek easily held off Creed to take the win in Stage 1, his third stage victory of the season.
Crafton was third, Busch advanced to fourth and Friesen rounded out the top-five.
Rhodes, who started on the pole, lost the lead in Turn 2 on the start to Creed.
On Lap 2, Roper spun off Turn 4 to bring out the first caution of the race. In those two laps, Busch, who started 29th, had made his way to 17th.
The race returned to green on Lap 7 with Creed leading the way. Nemechek quickly grabbed the lead on the restart.
With 15 laps to go in the first stage, Nemechek maintained a small but steady lead over Creed while Busch had advanced into the top-five.
With five laps remaining, Nemechek opened up a nearly 3-second lead over Creed with Crafton in third.
Kris Wright had to start the race from the rear of the field due to unapproved adjustments to his truck.