Ohn Joo-wan made his acting debut in 2004 with an appearance in the movie Flying Boys. In 2005, he landed the leading role in the film The Peter Pan Formula, which won him Best Actor at the 27th Dubai International Film Festival and Best New Actor at the 20th Golden Cinematography Awards. In 2016, he became part of the main cast of the SBS romantic comedy Beautiful Gong Shim, which earned him a Special Acting Award at the SBS Drama Awards. In 2017, he led the MBC drama Man Who Sets the Table, opposite Sooyoung. His performance in the series won him an Excellence Award at the 11th Korea Drama Awards. In 2021, he joined the cast of the megahit SBS drama Penthouse for its second and third seasons.

Ohn Joo-wan enlisted for his mandatory military service in October 2008 and was discharged in December 2010. He dated his Surplus Princess co-star Jo Boa for almost two years. They were confirmed to have broken up in January 2017.