Sadler denied Ricky Stenhouse Jr. a fourth straight victory at Iowa Speedway, and increased his lead in the series standings to 18 points over Austin Dillon.
Sadler won the pole with a track-record qualifying speed of 135.141 mph and was near or at the front of the pack the entire race. He overtook Justin Allgaier on the 192nd lap and went on to his fourth victory of the season.
Allgaier was second, followed by Sam Hornish Jr., Michael Annett and Stenhouse.
Danica Patrick finished 11th.
Hornish won the final "Dash4Cash" bonus of $100,000. His fan partner, Tammy Altieri of Spokane, Wash., also won $100,000.