Lee Young Hoon was born in Gwangju, South Korea. He began his acting career after joining the MBC Academy while in high school. Some of his peers at the MBC Academy were future actors Jo In Seong and Lee So Yeon.
In 2001, at the age of 19, Young Hoon was cast by Leesong Hee Il for his short film "Good Romance" as Won Kyu. Lee Young Hoon then entered Suwon Science College as a drama major and practiced and performed on stage at the university.
Young Hoon then served his mandatory 2-year military requirement. Upon his discharge, Leesong Hee Il cast Young Hoon in the independent film "No Regret" as Su Min. Young Hoon found the role difficult because it was 4 years since he last acted on film. "No Regret" became somewhat of a ground breaking film as it attempted to realistically portray the lifestyle of a gay man working in the male host industry. The film screened to packed audiences at the 2006 Pusan International Film Festival and became a hit in the film festival circuit as well as being widely praised by critics. Young Hoon would win the best newcomer award at The Critic's Choice Awards presented by the Korea Film Critics Society.

In 2008, Lee Young Hoon appeared in his first major commercial film "The Guard Post" as Corporal Kang Jin Won, as well as the romance film "Ride Away".