The 2009 NASCAR Nationwide Series was the 28th season of the NASCAR Nationwide Series, the second national stock car racing series sanctioned by NASCAR in the United States. The season began on February 14 at Daytona International Speedway with the Camping World 300. The season concluded on November 21 at Homestead–Miami Speedway with the Ford 300. With 25 top-five finishes, Kyle Busch was the season champion. He finished 210 points clear of Carl Edwards and 318 ahead of Brad Keselowski.

Before the start of the season, NASCAR changed restart rules regarding the final moments of all races in the Sprint Cup, Nationwide Series and Camping World Truck Series. Previously, when the race was inside the final ten laps, all cars/trucks on the lead lap were in a single-file restart in that window. As of the 2009 season, the window changed to the final 20 laps. The "lucky dog"/"free pass" rule was still be eliminated in the last ten laps of a race. This rule will not matter starting at the July Daytona race, with the addition of "Double-File Restarts Shootout Style."

After being successful in the NASCAR Sprint Cup Series, NASCAR will implement a double-file restart system starting at the July Daytona race. The entire field will line up double-file, much like the start of the race at every restart. The leaders and other lead lap cars are now in front always when taking the green flag. Cars who choose to stay out and not pit during a caution flag who are in front of the leaders are now waved-around to restart (double file) at the back of the field. The lucky dog/free pass rule is now in effect the entire distance of the race, and the double-file restarts are for every restart, including green-white-checkered finishes. The only reason cars do not line up double-file in the order they are position wise on the leaderboard is if they are serving a penalty (in most cases, for pit road violations). The leader of the race also has the option of selecting which lane, inside or outside, to restart in, however, the 3rd place car (and 5th, 7th, and so on) will always restart on the inside.

The Camping World 300 was held February 14 at Daytona International Speedway. Kevin Harvick took the pole but Tony Stewart won the race.

Did not qualify: Larry Foyt (#56), Johnny Chapman (#90), Stanton Barrett (#31), Terry Cook (#91), Derrike Cope (#41), Johnny Borneman, III (#22).

The Stater Brothers 300 was held February 21 at Auto Club Speedway. Carl Edwards took the pole but Kyle Busch won the race.

Did not qualify: Scott Wimmer (#40), Johnny Borneman, III (#22), Mike Harmon (#84), Andy Ponstein (#02).

The Sam's Town 300 was held February 28 at Las Vegas Motor Speedway. Scott Speed took the pole but Greg Biffle won the race.