Kim Won-seok began his television career in 2001 as an assistant director for the Korean Broadcasting System (KBS) network.

[9][10] Kim left KBS and in August 2011, he signed with media conglomerate CJ E&M, which owns cable channels Mnet and tvN.

[14] Auditions were held, and Kim cast rookie actress Ha Yeon-soo, K-pop singer Yong Jun-hyung and stage actor Kang Ha-neul in the lead roles.

"Incomplete Life") about a former baduk player who becomes an office temp worker at a trading company, it became one of the most anticipated Korean TV series of 2014.

[16] The workplace dramedy Misaeng had no A-list stars (its cast was led by Im Si-wan and Lee Sung-min[17][18][19]), but it struck a chord among viewers and critics, unexpectedly becoming a huge ratings hit for cable and a pop culture phenomenon.

[28] In January 2020, The JoongAng Ilbo published an exclusive report that stated Kim has joined Kakao M's soon-to-be-launched new drama production subsidiary to be led by former Studio Dragon and CJ E&M executive Park Ho-sik.