On October 15, 2018, it was announced that longtime sponsor Lilly Diabetes will be pulling out of NASCAR, leaving the Roush Fenway Racing No. 16 car unsponsored for 2019. On December 2, 2018, Ty Majeski said that RFR will not have an Xfinity program in 2019.
On November 17, 2018, Stewart-Haas Racing announced that they would run a second full time car in 2019. On November 27, 2018, Chase Briscoe was announced as the driver of the No. 98 Ford.
On December 21, 2018, Rick Ware Racing announced that they will field the No. 25 car full-time in 2019, beginning at Daytona in February.
On January 4, 2019, Chip Ganassi Racing suspended operations in the Xfinity Series due to a lack of sponsorship. The shutdown was announced after the home of the CEO of DC Solar, the team's primary sponsor, was raided by the FBI on December 18, 2018.
On August 15, 2018, Elliott Sadler announced his retirement from full-time competition, thus leaving the JR Motorsports No. 1 team open. It was announced on September 25 that Noah Gragson would replace Sadler, driving the No. 1 Chevrolet Camaro SS full time in 2019. On January 25, 2019, it was announced that Gragson would be driving the No. 9 car full-time in 2019.
On October 19, 2018, Spencer Gallagher announced that he would be retiring from racing at the end of the 2018 season and would take on a managerial role at GMS Racing. On December 6, 2018, it was announced that John Hunter Nemechek would replace Gallagher in the No. 23 Chevrolet.
On November 9, 2018, it was announced that Ross Chastain would join Chip Ganassi Racing to drive the No. 42 Chevrolet full-time in 2019. However, following an FBI raid on DC Solar's headquarters in December 2018, it was announced on January 4, 2019, that Chip Ganassi Racing would withdraw from the Xfinity series before the start of the 2019 season. Chastain solidified his plans on January 31, 2019, when he joined Kaulig Racing for three races in the organization's No. 10 car and went back to his old ride at JD Motorsports for the other 30 races on the schedule.
On November 29, 2018, it was announced that Chase Briscoe would join Stewart-Haas Racing with Biagi-DenBeste to drive the No. 98 Ford full-time in 2019, while also competing for Rookie of the Year honors. In 2018, Briscoe drove a part-time schedule in the Xfinity Series, splitting time between the No. 98 and the No. 60 Roush Fenway Racing Ford.
On December 1, 2018, it was announced that Justin Haley would join Kaulig Racing to replace Ryan Truex in the No. 11 Chevrolet. Haley will also compete for Rookie of the Year Honors. Truex has since moved to a part time ride in the No. 8 for JR Motorsports. In 2018, Haley drove the No. 24 GMS Racing Chevrolet Silverado in the NASCAR Camping World Truck Series while also making a few starts in the Xfinity series.
On December 2, 2018, Ty Majeski announced that he will be returning to Super Late Model racing in 2019 after it was revealed that Roush Fenway Racing will shut down its Xfinity program.
On December 4, 2018, it was announced that Blake Koch would make his Xfinity series return by driving the JD Motorsports No. 4 Chevrolet full-time in 2019. On January 31, 2019, Koch announced that he would step away from racing to focus on his business Filter Time. Koch's seat was filled by Ross Chastain for the majority of the schedule.
On December 18, 2018, it was announced that Zane Smith would join JR Motorsports for eight races in the organization's No. 9 car with additional drivers to be announced at a later date. Smith drove in the ARCA Racing Series in 2018, finishing 2nd in final points. On January 25, 2019, it was announced that Smith would share the new No. 8 Chevrolet with Brett Moffitt, Ryan Preece, Ryan Truex, Chase Elliott, Dale Earnhardt Jr. and Jeb Burton.
On November 17, 2018, it was announced that two-time defending series champion crew chief Dave Elenz will move to the No. 1 JR Motorsports Chevrolet with rookie Noah Gragson in 2019. On January 7, 2019, it was announced that his replacement for the No. 9 team will be Taylor Moyer. On January 25th, 2019, it was announced that Dave Elenz will be the crew chief for the No. 9 Chevrolet with Noah Gragson while Taylor Moyer will be the crew chief for the No. 8 JR Motorsports Chevrolet.
On December 6, 2018, Joe Gibbs Racing announced that Jeff Meendering will replace Chris Gabehart as crew chief of the No. 19 Toyota, as Gabehart has been promoted to Denny Hamlin's crew chief in the MENCS. Ben Beshore replaces Eric Phillips as crew chief of the No. 18 team, as Phillips moves to the MENCS as the No. 11 car chief.
Before the 2018 Homestead race week, MBM Motorsports announced that they were selling their Chevrolet and Dodge Xfinity cars and intends to use Toyota bodies only for the 2019 season. They previously ran cars from all four manufacturers at some point throughout the 2018 season. It is unknown how many cars they will field, although Chad Finchum is expected to stay with the team for 2019.
With the new flange-fit composite bodies being made mandatory in the 2019 season, Dodge left the Xfinity Series after the 2018 season, as the former Team PenskeChallengers (nicknamed "Zombie Dodges" due to their lack of factory support since 2013) used by smaller teams were deemed ineligible due to their steel bodies. This also means that Dodge would have no representation in NASCAR's three major series for the first time since 1994.
On August 23, 2018, NASCAR announced that Cup drivers competing in Xfinity Series events would no longer be eligible to earn playoff bonus points for the cars that they were driving.
On the same day, a change in the number of cars in the field was changed, going from 40 to 38.
The flange-fit composite bodies, first introduced in 2018, will be made mandatory for all races in the 2019 season.
On February 4, 2019, NASCAR announced a new post-race inspection rule in all three series, where race-winning teams found to be in violation of the rule book will automatically be disqualified. Following a race, the first-place and second-place teams, along with at least one randomly selected car, will undergo post-race inspection. The inspection should take between 90 minutes and two hours to complete before the race winner is officially declared. The car that fails the inspection will receive last-place points and will be stripped of playoff and stage points.
On February 4, 2019, NASCAR announced a change in the qualifying schedule procedures for the majority of its tracks. For short tracks and intermediate speedways, the first round will be shortened from 15 minutes to 10 minutes, while the second and third rounds will remain at 10 and five minutes, respectively. The downtime intervals at all tracks will be reduced from seven minutes to five minutes. Superspeedway qualifications will retain their untimed two-round intervals of single-lap qualifying while road courses will continue to use two qualifying rounds: 25 minutes for the first round and 10 minutes for the final round.
The schedule, consisting of 33 races, was announced on June 13, 2018. Similar to the Monster Energy Cup Schedule, there are no changes from 2018 to 2019; However, both the regular-season finale at Las Vegas and the playoff race at Texas will be night races.
Bonus money Dash 4 Cash races indicated in BOLD. Qualifying race for first Dash 4 Cash race in Italics.