Kenseth started racing on several short tracks in Wisconsin and he won track championships at Madison International Speedway, Slinger Super Speedway and Wisconsin International Raceway. He moved to the ARTGO, American Speed Association, and Hooters Late Model touring series before getting a full-time ride in the NASCAR Busch Series (now Nationwide Series) for his former Wisconsin short track rival Robbie Reiser. After finishing second and third in the Busch Series (now Nationwide Series), he moved up in the NASCAR Winston Cup Series (later NEXTEL Cup Series and now Sprint Cup Series). He won the series' Rookie of the Year title in 2000 and the championship in 2003. The International Race of Champions invited Kenseth to race in their 2004 season as the reigning champion and he won the season championship.

In 2009, he won a rain-shortened Daytona 500. He repeated as Daytona 500 winner in 2012. He has over 220 top tens and over 20 wins in NASCAR.