Kim Joon-han began his entertainment career as the drummer of the South Korean modern rock band izi, which debuted in 2005. In 2014, he landed a supporting role in the horror movie Navigation. He then tried his hand at directing with the 2015 short film Frog. In 2016, he starred in the indie film Greet, where he was also credited as screenwriter. His work in the movie won him Best Actor at the 16th Jeonbuk Independent Film Festival. In 2017, he played a Japanese judge in director Lee Jun-ik’s biographical period drama film Anarchist from Colony, which earned him numerous Best New Actor nominations. That same year, he made his television debut with a role in tvN’s Smart Prison Living. He next appeared in the 2018 drama film Herstory, which gave him two more Best New Actor nominations. He was also nominated from an Excellence Award at the 2018 MBC Drama Awards for Time. In 2019, he acted alongside Han Ji-min and Jung Hae-in in the MBC romantic drama One Spring Night, which scored him another Excellence Award nomination at the MBC Drama Awards. In 2020, he became part of the popular tvN series Hospital Playlist.

Kim Joon-han attended Woosong Information College.