An alumnus of the legendary theater troupe Mokhwa, Im Won-hee made his big screen debut in director Jang Jin’s 1998 black comedy The Happenings. He has since appeared in numerous movies and television dramas, including the hit action comedy short film Dachimawa Lee in 2000, in which he played the titular character. In 2007, he starred in the manhwa-based film Le Grand Chef along with Kim Kang-woo and Lee Hana. His work in the movie earned him a Best Supporting Actor nomination at the 29th Blue Dragon Film Awards. In 2008, he was cast to reprise the iconic titular role in the feature film remake of Dachimawa Lee. In 2016, he was nominated for a Special Acting Award at the SBS Drama Awards for his performance in Romantic Doctor Teacher Kim. In 2018, he took home the Best Entertainer trophy at the SBS Entertainment Awards for My Little Old Boy.  That same year, he became part of the SBS series Greasy Melo, which won him Best Supporting Actor at the SBS Drama Awards.

Im Won-hee married a stage actress in 2011 after dating for over a year. They divorced in 2014.