Dietzen, who started 32 games for the Badgers, announced his decision Monday on Twitter.
He started 12 games at left tackle for Wisconsin in 2018, missing one contest because of injury. Dietzen battled ankle and hip injuries throughout the 2017 season, and underwent surgery before the 2018 season to repair labrum tears in both hips.
"This was not an easy decision, as I have enjoyed every second of my football career, especially those as a Wisconsin Badger," Dietzen wrote.
His retirement means Wisconsin will return only one starting offensive lineman, center Tyler Biadasz, in 2019. Guards Michael Deiter and Beau Benzschawel both exhausted their eligibility, and right tackle David Edwards entered the NFL draft with a year of eligibility remaining.