His dad, John Alt, played offensive tackle between 1984-1996 with the Kansas City Chiefs. His brother, Mark, is a defenseman in the NHL for the Colorado Avalanche.
Joe Alt was rated as a 3-star recruit by ESPN and handed a 4-star rating by 247 Sports out of Totino-Grace High School in Minnesota. Alt decided to join Notre Dame and was considered a tight end-tackle as a freshman.
In Alt’s freshman season, he played in 11 games and played a total of 613 snaps. He was credited with allowing 3 quarterback sacks and one quarterback hit playing left tackle.
In 2022, Alt made some mechanical and stance adjustments and became one of the country's best left tackles. In 12 games, he was on the field for 807 snaps and he only conceded 3 hurries and 2 quarterback hits. Alt did not allow a sack in 2022 playing left tackle. He was rock steady in 2023 once again. He did give up his first sack in 2 seasons, but the majority of the time he dominated.