Lee Sun-kyun entered the Korea National University of Arts in 1994, and graduated in the first ever batch of its School of Drama. In 2001, he made his acting debut as Brad Majors in the stage musical The Rocky Horror Show.

Playing small supporting roles for many years, he eventually achieved his breakthrough in 2007 with the critically lauded medical drama White Tower and the highly popular romantic series Coffee Prince. Besides Coffee Prince, he has worked with director Lee Yoon-jung two other times—in the sports-themed Taereung National Village in 2005, and in slice-of-life drama Triple in 2009.

Lee was appointed as ambassador for the Health Insurance Review Agency in 2007, and won an award from the Korea Advertisers Association in 2008.

Lee was born in Seoul, South Korea. He married his girlfriend of seven years, actress Jeon Hye-jin on May 23, 2009.

Their sons were born on November 25, 2009, and August 9, 2011.

In 2012, he starred in two consecutive well-reviewed big-screen hits—mystery thriller Helpless and romantic comedy All About My Wife. Reuniting with Pasta director Kwon Seok-jang, Lee played a trauma doctor in Golden Time. His third collaboration with Kwon was Miss Korea, a drama set amidst the IMF crisis in the 1990s.

Lee returned to the theater opposite wife Jeon Hye-jin in Mike Bartlett’s stage play Love, Love, Love in 2013. The following year, he headlined the film A Hard Day, which screened at the Directors’ Fortnight section of the 2014 Cannes Film Festival, and became a critically acclaimed sleeper hit at the box office. In 2015, Lee starred in courtroom drama film The Advocate: A Missing Body.

In 2018, Lee starred in the critically acclaimed television series My Mister. The same year he starred in the action thriller film Take Point.

In 2019, Lee is set to star in the legal television series Prosecutor Civil War.