Kim Kyung-nam acted a small role in the 2012 SBS fusion medical sageuk series Faith. In 2017, he landed more significant roles in the KBS2 drama Strongest Deliveryman and in tvN’s Smart Prison Living. In 2018, he was cast as the older brother of Jang Ki-yong’s character in the MBC romantic melodrama Come Here and Hug Me. His work in the series won him Best New Actor at the 2018 MBC Drama Awards. He also bagged the Best Supporting Actor trophy at the 2018 SBS Drama Awards for his performance in the series Fox Bride Star. Also in 2018, he had a minor role in the thriller film The Discloser. In 2019, he became part of the main cast of the MBC drama Special Labor Inspector Jo. His work in the series earned him a nomination for an Excellence Award at the 2019 MBC Drama Awards. In 2020, he starred in the hit SBS romantic fantasy The King: Eternal Monarch.

Kim Kyung-nam is good friends with his fellow actors Jang Ki-yong and Woo Do-hwan.