Sadler didn't pit during the final caution to inherit the lead, and was out front on the final restart with 28 laps to go in Saturday's race.
He easily held off Kasey Kahne and Brad Keselowski to win for the second time in three weeks. Prior to this winning streak, Sadler's last victory in the Nationwide Series came in 1998.
Kahne finished second, Keselowski was third and was followed by Joey Logano and Dale Earnhardt Jr.
All four Nationwide races this season have been won by drivers who don't compete in the elite Sprint Cup Series. It marks the first time since 1995 Cup drivers have been shut out over the first month of the season.