Kim Sang-kyung made his screen debut with a small role in the 1998 film If the Sun Rises in the West. In 1999, he was named Best New Actor at the MBC Drama Awards for the series Last War. In 2002, he starred in director Hong Sang-soo’s Turning Gate, which gave him another Best New Actor trophy at the 10th Chunsa Film Awards. He next appeared in director Bong Joon-ho’s crime-thriller film Memories of Murder. In 2007, he led the movie May 18, which earned him a Best Actor nomination at the 28th Blue Dragon Film Awards. In 2008, he took on the titular character in the KBS sageuk The Great King, Sejong. In 2014, he bagged an Excellence Award at the KBS Drama Awards for the weekend drama What’s With This Family. In 2018, he was given the Jury Special Award at the 38th Golden Cinematography Awards for the thriller film The Discloser. In 2019, he joined the main cast of the tvN sageuk The Crowned Clown, which scored him a Best Supporting Actor nomination at the 55th Baeksang Arts Awards. In 2021, he was nominated for a Top Excellence Award at the SBS Drama Awards for his role as a badminton coach in the sports drama Racket Boys.

Kim Sang-kyung married a dentist named Kim Eun-kyung in October 2007. They have two sons together.