When Lee Je-hoon realized that he wanted to go into acting, the Biotechnology major at Korea University dropped out and transferred to the School of Drama at Korea National University of Arts. From 2006 to 2010, Lee appeared in more than 18 student shorts and indie films, notably queer coming-of-age romance Just Friends? He also appeared as an extra in a number of commercial films, including erotic thriller The Servant and romantic comedy Finding Mr. Destiny.

Then Lee had his breakthrough in 2011. He received critical raves for his performances as a manipulative alpha-male in the haunting indie Bleak Night, and as a morphine-addicted squad leader in big-budget war film The Front Line. He gained mainstream popularity as a shy college student pining for his first love in box-office hit Architecture 101, and though the television series Fashion King was poorly received, his role as a struggling young chaebol heir in Korea’s fashion industry further showcased his versatility.

Lee next starred opposite acclaimed veteran actor Han Suk-kyu in the comedy-drama My Paparotti, which focuses on the special relationship between a high school gang member who dreams of becoming a singer like the late tenor Luciano Pavarotti, and the music teacher who helps him pursue his dream. After doing the promotions for Ghost Sweepers, dubbing the character Jack Frost for the Korean release of 3D animated film Rise of the Guardians, then filming My Paparotti and An Ethics Lesson, Lee enlisted on October 25, 2012 for his mandatory military service as a member of the Seoul Metropolitan Police Agency riot police. He was discharged on July 24, 2014.

For his comeback project, Lee chose Secret Door, a period drama about Crown Prince Sado who was controversially executed through death by starvation by his father King Yeongjo; the series reunited him with Han Suk-kyu. This will be followed by the Jo Sung-hee-directed film Detective Hong Gil-dong, a modern retelling of the eponymous folk hero as a private detective in the 1990s.