His musical career began in 2011 as a contestant in the first installation of K-pop Star (2011–2012); where he caught the attention of YG Entertainment CEO Yang Hyun-suk and was signed under his agency.

[8] Lee then formed the dance team "Honest Boys" (바른아이들; baleun aideul) with friends from Busan and showcased their performances on the streets of Seoul.

[11][14] BoA voiced her desire to work with him while JYP Entertainment CEO Park Jin-young stated Lee was the only contestant he viewed as a "true artist".

[1] On February 25, 2013, YG Entertainment CEO Yang Hyun-suk stated Lee would shine best in a boy band contrary to as a soloist thus his preparation for debut in their upcoming team; however, he participated as a contestant for WIN: Who is Next?

(2013) which involved two assembles consisting of male trainees under the label (A and B) who would battle for the chance to debut by series end after embarking on a one-hundred day journey.

[32][33] On February 28, 2023, it was announced that Lee was confirmed to be cast in the stage musical Dream High as one of the lead character roles, Song Sam-Dong, along with actor Eum Moon-suk and SF9 member Yoo Taeyang.

[37][33] As a dancer, Lee's style is considered more relaxed compared to the usual vigorous movements found in most idols, as he puts more detailed elements in his choreography with accordance to its lyrics or sound.

[39] Kwon Young-deuk of YGX stated Lee fully immerses himself and "feels" the dance and also learns choreography the fastest in YG Entertainment.

[40] For Winner, Lee has choreographed their debut lead singles "Empty" (공허해; gongheohae) and "Color Ring" from 2014 S/S and "Fool" from Fate Number For – which he created and finalized within five hours.

[41][42] In September 2017, Lee and his bandmate Mino were chosen as the influencers most suited in becoming ambassadors of the luxury brand, Burberry, appointed by its previous creative officer Christopher Bailey as they exhibited a "Viktor Horsting & Rolf Snoeren-like approach to haute couture".

Both were labelled as winning front row looks and acquired advance access to the Burberry Spring 2018 collection two days after they landed at Heathrow Airport in London.