The Oscar-nominated actor, 46, will appear on an upcoming episode in which Claire (Julie Bowen) learns her ex has become good friends with her mom, DeDe. Shelley Long, who originated the role of the former Mrs. Pritchett last season, will return in the same episode.
An airdate for the episode has not been scheduled.
Dillon is best known for his roles in the films Crash and There's Something About Mary. He most recently appeared in Takers.