The most decorated Olympian in history will play himself on the episode, scheduled to air at 9 p.m.
Phelps' IMDb page also includes a 2008 appearance on HBO's "Entourage" in which he played, you guessed it, himself.
The "Suits" appearance comes after several months of relative quiet for the retired swimmer, who spurred comeback speculation last year by re-entering the drug testing pool for international competition. Though Phelps has worked out with his longtime coach Bob Bowman, he has made no definitive statements about future plans for swimming.
A representative said Phelps wasn't available for an interview this week.