In 2006, General Motors created a driver developmental search program wherein they looked for individuals they believed to be the stars of the future and invited them to test a late model and a Busch car at two different tracks with the best moving on. Earnhardt made the final cut. In 2007, Earnhardt drove the No. 1 Chevrolet for Andy Santerre Motorsports in the NASCAR Busch East Series. He finished fifth in the 2007 Busch East point standings and won the Most Popular Driver Award at the end of the season.

In 2008, Earnhardt returned to what is now known as the ARCA Menards Series East for another full season, along with selected Nationwide Series races. Earnhardt was unexpectedly replaced in the car at Dover in September 2008 with Aric Almirola who won the race. When DEI subsequently merged with Chip Ganassi Racing, their driver development program went into limbo, and Earnhardt was released.

In 2010, Earnhardt drove several races with Rick Ware Racing which qualified him to drive on all NASCAR tracks in the 2011 season. He signed with RWR to drive a full season in 2011 and make his run for rookie of the year in the NASCAR Camping World Truck Series. However, he was originally released from the team after offering his driving services to other truck teams. Earnhardt and Ware later reconciled, citing a lack of communication from both parties. RWR ran Earnhardt in the 24 Hours of Daytona where they finished 12th.

Earnhardt moved to the grand-am Rolex Sports Car Series in 2012, where he raced in the GT class for Rick Ware Racing.

In November 2012, he announced he would be competing for rookie of the year in the NASCAR Nationwide Series in 2013, driving the No. 79 for Go Green Racing; sponsorship issues later limited his schedule with the team.

Earnhardt made his amateur debut in mixed martial arts on May 22, 2012, defeating Chris Faison by unanimous decision in Charlotte, North Carolina.

On April 4, 2013, it was announced that Earnhardt would drive the No. 5 Chevrolet Camaro for JR Motorsports in a one-race agreement for the Nationwide race at Richmond International Raceway.

In the 2013 Charlotte testing for Sprint Cup cars, Earnhardt tested a car for Go Green Racing.

For 2014, Earnhardt moved full-time to the Nationwide Series, driving the No. 4 Chevrolet for JD Motorsports. During the Subway Firecracker 250 at Daytona, he was replaced by Matt DiBenedetto during the first caution period, since Earnhardt had suffered a fractured collarbone in a motorcycle accident during the week. His car was sponsored by The Great Outdoors RV Superstore for the Nationwide series Zippo 200 race at Watkins Glen International where he finished 21st. He would then finish 18th in the point standings and was also released by JD Motorsports after his disappointing season.

Before the 2015 season started, Earnhardt was picked up by Viva Motorsports to drive the season opener at Daytona. He finished 15th in the Daytona race.

After the 2016 season ended, Go Fas Racing announced that Earnhardt would not return to the No. 32 team for 2017, and was replaced by Matt DiBenedetto. In January 2017, Earnhardt announced that he would drive the No. 33 Chevrolet for Circle Sport – The Motorsports Group. The following month, Earnhardt made his CS–TMG debut at the Daytona 500, and in his debut with the team, Earnhardt made NASCAR history by becoming the first-ever fourth-generation driver to compete in the Daytona 500. He started 33rd and finished 26th (which tied his career best finish up to that point) after being involved in a crash on lap 143. Earnhardt raced the full season except for the road courses. Starter sponsored the early part of the season, while Hulu stepped in to sponsor the majority.

On October 15, 2017, Earnhardt signed a contract extension to remain with CS–TMG for the 2018 season. However, on December 12, Circle Sport Racing and The Motorsports Group ended their partnership, leaving Earnhardt temporarily without a ride. Earnhardt ended up joining the No. 00 StarCom Racing team for the 2018 Daytona 500, marking the 40th consecutive year that a member of the Earnhardt family had driven in the event. Earnhardt also ran the next four races for StarCom and planned to run the full season for the team, but after the fifth race of the season, he and the team parted ways. On May 22, it was announced that Earnhardt would drive the No. 55 for Premium Motorsports in Charlotte’s Coca-Cola 600. The week following the race, he announced more races with the team but did not name an exact number. On July 7, Earnhardt finished 11th at the Coke Zero Sugar 400, which was his career best Cup Series finish up to that point. On July 28, 2018, it was announced that Earnhardt would join Gaunt Brothers Racing in their No. 96 Toyota for 14 races, with sponsorship from Xtreme Concepts.

In November 2018, Earnhardt joined Joe Gibbs Racing’s for the 2019 NASCAR Xfinity Series season, driving the No. 18 Toyota Supra in nine races and sharing the ride with Riley Herbst, Kyle Busch, and Denny Hamlin. At the summer Charlotte race, Earnhardt scored a career-best third place finish, despite sustaining damage from hitting the turn 3 wall on lap 142.

On February 14, 2019, security company and sponsor Xtreme Concepts announced the formation of XCI Racing, which would field the No. 81 Toyota Camry and Supra for Earnhardt at the two Talladega Cup and five Xfinity races, respectively. Earnhardt has stated that he would like to build with XCI to a full season in NASCAR’s premier series in 2020. On July 3, XCI and Earnhardt had withdrawn from the 2019 Circle K Firecracker 250. On August 7, Earnhardt publicly announced that he and XCI parted ways before the 2019 B&L Transport 170 and will no longer drive for both XCI and Joe Gibbs Racing.

Earnhardt returned to JD Motorsports in 2020 on a 12-race schedule.