Lee Tae-sun made his television debut in the 2016 romantic comedy Entertainer where he portrayed a single dad and bassist of a band.

[1] The following year, he was cast in Queen of the Ring, which is the third installment of the Three Color Fantasy trilogy, and in the black comedy Prison Playbook, in which he played the younger version of Park Hae-soo's character.

[4] He also took on the role of an elite lawyer in Suits, adapted from the American television series of the same name, and a bar owner as well as the male lead's childhood friend in Gangnam Beauty.

[5][6] In 2019, Lee appeared in Hotel del Luna, playing IU's character's best friend Yeon-woo in his past life and police officer Park Young-soo in his current life, for which he gained recognition.

[8][9] In 2020, Lee appeared on tvN's travel show RUN alongside Ji Sung, Kang Ki-young and Hwang Hee, and on SBS's basketball reality show program Handsome Tigers.