[1][2] Under the stage name Yoo Gun, he began his entertainment career in 1997 as a singer in South Korean boy band Oppa.

Supporting roles followed in the comedy films Dasepo Naughty Girls, Project Makeover, Mission Possible: Kidnapping Granny K, and My Mighty Princess.

[3][4] Yoo underwent six months of martial arts training for his next leading role in the action drama Fight, which aired on cable in 2008.

[5] Besides appearing in the TV series Bad Couple, Can't Stop Now, and Prosecutor Princess, he also made his theater debut in 2010 in the stage play Thief's Diary.

After his discharge in December 2012, Yoo quickly resumed his career, appearing on the travel program The World is Delicious (오감만족 세상은 맛있다) in an episode about Brazil,[9] followed by a cameo on the melodrama That Winter, the Wind Blows.