Joon is a member of the Korean group MBLAQ. He was an actor for commercials before he joined the group. He had a small role in the Korean sitcom "That person is coming". In 2009 Joon also appeared in "Ninja Assassin" as the teenage Raizo. He then became a part of the boy band MBLAQ.In 2010, he has been cast in two dramas, titled "Jungle Fish 2", in which he will play opposite JiYeon from T-ara, and also "Stay-at home-mom Kim Kwang Ja", also known as Housewife Kim Kwang Ja's third activity, which aired on the 22nd of September 2010.He is a singer signed to J.Tune Entertainment, where he is one of the five members of Korean boy band MBLAQ, active in South Korea.