He was then cast as Yoo Han-yang, a second-generation tycoon serving in prison for drug use, in tvN's television series Prison Playbook (2017). In 2017, he played the role of Yoon Se-won, chief of the prosecution's investigation team, in the tvN drama Stranger, raising his profile. In 2013, he appeared in the film The Face Reader after receiving a phone call from a friend that the actor slated to appear had a flat tire and couldn't come to set. He has since starred in various plays and musicals, most notably with recurring roles in Laundry, Fan Letter, and Gloomy Day.
Lee made his film debut in 2001 with a minor role in the movie Kick the Moon. After graduating, he continued to act in theater, as well as appearing in musicals. Lee Kyu-hyung began his acting career in the Seoul Metropolitan Police Agency's " Whistle Theater " whilst attending college and completing his mandatory military service. Lee made the decision to transfer to Dongguk as it was the alma mater of Choi Min-sik, an actor he admired. He was accepted into Kyung Hee University's film and theatre department, but dropped out before completing his degree and later graduated from Dongguk University with a major in Theater Studies. Lee attended Joongdong High School in Seoul, where he was a part of the theatre club. Lee's interest in acting was inspired by the 1999 Korean film Shiri, and he began to pursue roles in theater in hopes of becoming a movie star.
His family consists of his parents and an older sister. Lee Kyu-hyung was born on November 29, 1983, in Seoul, South Korea.