Kenseth became the first driver since Jeff Gordon in 2005 to take a second Daytona 500 title, besting Dale Earnhardt Jr. by 0.21 seconds in a marathon affair that had been rescheduled from Sunday due to rain.
Kenseth led for 50 for the 203 laps in the Sprint Cup season opener and used an assist from Roush Fenway Racing teammate Greg Biffle to block out Earnhardt during the final two overtime laps and pull off the win.
It was tight in the last few laps, with 12 cars within a second of each other before the final caution.
Biffle finished third at 0.26 seconds off the pace, followed by Danny Hamlin in fourth and Jeff Burton in fifth.
The race was halted after 160 laps when Juan Pablo Montoya's car crashed into a jet drying vehicle, causing a massive fire on the track. While the drivers were under caution with 40 laps left Montoya, speeding along the backstretch, lost control and slid into the back of the jet dryer.
The truck, loaded with jet fuel, erupted into a smoky fire, with burning fuel spilling onto the track.
Montoya escaped from his car and the driver of dryer truck was hospitalized for observation.
NASCAR officials halted the race as crews put out the flames. A lengthy inspection of track followed in a delay that lasted 2 hours, 5 minutes.
Blaney was leading the race at the time of the crash.
The mishap came after rain had washed out Sunday's scheduled start. The race had been rescheduled for noon Monday and then was pushed back to a 7 p.m. start.