It was redemption for Smith, who was leading on the last lap a year ago when he tried to block Keselowski to preserve the win. It triggered a 12-car accident that sent Kyle Larson's car into the fence. Nearly 30 fans were injured from debris that sailed into the grandstands.
The win was Smith's fourth career victory in the Nationwide Series, but first at Daytona.
Keselowski finished second, .013 seconds behind. The finish was the second-closest at Daytona International Speedway and seventh closest in series history.
Trevor Bayne was third.
Kyle Busch, winner of Friday night's Truck Series race, was fourth and his Joe Gibbs Racing teammate Elliott Sadler was fifth.