Tune Entertainment, Lee became a member of South Korean quintet boyband MBLAQ, serving as a vocalist and main dancer.

The group debuted on October 9, 2009 at Rain's Legend of Rainism concert where they performed various songs from their then-unreleased single album Just BLAQ.

[6] MBLAQ made their Japanese debut on May 3, 2011, with an event held at the Kanagawa Lazona Kawasaki Plaza which gathered a reported 10,000 fans.

A day later, on May 4, they released their first Japanese single "Your Luv" which immediately reached first position of the Oricon Daily Charts, selling more than 11,000 copies.

[9][10] On October 18, 2017 ahead of his mandatory military enlistment Lee released his first solo digital single, "What I Want to Give to You", a pop ballad song written by his former MBLAQ band-mate Thunder.

[12] He participated in the OST for Jungle Fish 2, singing the song "슬픈예감 (Feeling Sad)" with Hong Jong-hyun.

[16] The film was unusually risque for a pop idol due to the numerous nude sex scenes he had to perform in it.

In 2014, Lee had roles in the crime thriller Gap-dong and romance comedy fantasy drama Mr.

In The Escape of the Seven Lee plays the role of Min Do Hyuk who used to be a gangster whose life is filled with a series of betrayals.

[34] Lee began his mandatory military service as an active duty soldier on October 24, 2017, attending a five-week basic training in Pocheon, Gyeonggi Province.