Leo debuted as a member of the South Korean boy group VIXX in May 2012,[2] and began his acting career in 2014 in the musical Full House as Lee Young-jae.

Leo studied music composition at Baekseok University and was a member of the National Youth Soccer Players from 2004 to 2007.

[11][12] During MyDOL, Leo was featured in Brian Joo's "Let This Die" and Seo In-guk's "Shake It Up" music videos.

[13][14] After his debut with VIXX, Leo appeared in episode 4 of SBS' television drama The Heirs alongside his group members.

[4] In 2015, Leo composed the song "On a Cold Night" (Korean: 차가운 밤에) for VIXX's fifth single album Boys' Record.

[21][22] In 2016 Leo was cast in the musical Mata Hari in the lead role of Armand from March 25 to June 12 at the Blue Square in Seoul.

[25] Leo was cast in the musical Monte Cristo in the supporting role of Albert from November 19, 2016, to February 12, 2017, at the Chungmu Arts Center Grand Theater.