On October 28, 2019, K&N Pro Series East team owner Sam Hunt announced that his Sam Hunt Racing would move up to the Xfinity Series in 2020, bringing driver Colin Garrett along with him. The team's schedule is estimated at about five races depending on how much sponsorship the team's crowdfunding model generated.
On October 15, 2019, it was announced that Ross Chastain will be driving for Kaulig Racing full-time in 2020 in their No. 10 car after running part-time for the team in 2019. In that announcement, the team also confirmed that Justin Haley would be returning to drive the No. 11.
On October 17, 2019, it was announced that Harrison Burton would be driving for Joe Gibbs Racing full-time in 2020 in their No. 20 Toyota, replacing Christopher Bell while also competing for Rookie of the Year honors. In 2019, Burton drove full-time in the NASCAR Gander Outdoors Truck Series driving the No. 18 Toyota Tundra for Kyle Busch Motorsports while also making some limited starts in the Xfinity Series, driving the No. 18 Toyota for Gibbs.
On October 18, 2019, Kaulig Racing president Chris Rice announced that the team intended on fielding their No. 16 car part time in 2020, with the tentative plan being for A. J. Allmendinger to return for all the road course races plus the new Martinsville race in October. Rice also stated they will field the car at the restrictor plate races, but they have not yet decided on a driver.
On October 31, 2019, it was announced that Brandon Jones signed a contract extension with Joe Gibbs Racing to drive the No. 19 Toyota through 2020.
On November 5, 2019, it was announced that Riley Herbst will drive the No. 18 Toyota full-time for Joe Gibbs Racing in 2020.
On November 5, 2019, Richard Childress Racing announced that Randall Burnett would be moving up with from the No. 2 team to the No. 8 RCR Cup car, continuing to work with driver Tyler Reddick as he takes over that ride next year, meaning he will vacate his position as crew chief of the No. 2 NXS car in 2020.
On November 7, 2019, Joe Gibbs Racing announced their crew chief lineup for 2020 with Dave Rogers returning to Handle Crew Chief duties for the number 18 car driven by Riley Herbst with Jeff Meendering Returning as crew chief for the number 19 car driven by Brandon Jones and Ben Beshore replaces Jason Ratcliff as crew chief of the No. 20 team, as Ratcliff moves to the MENCS as the No. 95 crew chief driven by Christopher Bell.
NASCAR Cup Series drivers will only be allowed to compete in five races, down from seven in 2019. Similar to 2019, Cup drivers are not allowed to compete in Dash 4 Cash or NASCAR playoffs races. Unlike 2019, the rule now applies to drivers declaring for Cup Series points with three or more years of Cup Series experience, down from five years of experience in 2019.
The Xfinity Series field will be reduced to 36 cars in 2020, down from 38 in 2019.
The Rinnai 250 at Atlanta will no longer be the second race of the season and moves a month later to become the fifth race of the season, and also the first race after the West Coast swing.
The order of races in the West Coast swing changes, with the series now going to Auto Club Speedway (Fontana) before ISM Raceway (Phoenix) instead of the other way around as it had been in the past. Because there will be no race in between Daytona and the West Coast swing, Las Vegas will now be the second race of the season (instead of the third) and the flip-flop of California and Phoenix will be the third and fourth races. (ISM had been the fourth race previously and now is still the fourth race after this switch.)
After being the season-finale for the Xfinity Series since 1995 and all three national series since 2002, Homestead-Miami Speedway lost its place as the last race of the season and will instead have its race in March between Atlanta and Texas on a weekend that had previously been an off weekend which will now be in April the week after Bristol.
After previously having two races on the schedule, Richmond lost its spring date in favor of a race at Martinsville in October, which marks the series' first trip to the track in 14 years, when it hosted a race for one year in 2006 (in between when the series stopped going to Pikes Peak after 2005 and started going to Montreal in 2007). The race at Martinsville in October will be the second-to-last race of the season and the last race of the Round of 8 in the playoffs. The Gander Outdoors Truck Series will now race on the spring weekend at Richmond instead, while Martinsville will only hold one truck race.
After being held sometime in August every year it has been on the schedule, Mid-Ohio moves earlier in the season to become the first race held after Charlotte on Memorial Day weekend, replacing Pocono.
The Pocono Green 250 at Pocono will be held on the last week of June, replacing Chicagoland. The race will be held on a Sunday afternoon instead of Saturday afternoon as part of the new "doubleheader-weekend" where the Cup Series will run both of their races at the track on the same weekend on consecutive days (on Saturday in addition to the Truck Series and Sunday in addition to the Xfinity Series).
The Camping World 300 at Chicagoland moves a week earlier than it was in 2019. It now falls on Father's Day weekend, which had previously been an off-weekend for the series, and that off-weekend was moved to July after the race at New Hampshire, as NBC will start their half of the season earlier.
After having hosted a night race on the Fourth of July weekend since 2002 in the Xfinity Series, Daytona's summer race will now be in August, trading places with Indianapolis.
The Use Your Melon Drive Sober 200 at Dover was knocked out of the playoffs and into the regular season as a result of Bristol being put in. That race at Dover will now be held on August 22 (the weekend where Road America had been).
Since Labor Day falls later in the year in 2020, the race at Daytona (Indy in 2019) will now be held before Darlington instead of after so Darlington can remain on Labor Day weekend.
The Charlotte Roval race is now later in the fall and in October instead of September.
After being the second-to-last race of the season for many years, ISM Raceway (Phoenix) will be the last race of the season after Homestead was bumped back to March. However, because of how the schedule works (only one off-weekend in the playoffs instead of two), it will remain on the same weekend in early November, and the season will end a week earlier than in the past.