Kim' first leading role came with critically appraised 2001 horror film Sorum, the feature debut of the director Yoon Jong-chan, telling the story of a taxi driver moving into a decrepit building that hides several dark secrets.

[10] A turning point came in his career when he was given the opportunity to play the lead role in the 2004-2005 historical drama Immortal Admiral Yi Sun-sin after producers viewed his work in More Beautiful than a Flower.

Kim was then cast in leading roles, playing a comical ex-gangster in Bad Family and a detective in Open City.

[15][16] White Tower was a critical and ratings hit in South Korea, gaining praise for its acting (particularly by Kim), writing, direction, and its intelligent and uncompromising story without concessions to melodrama or romance.

Subsequently, his performance as a maestro in the 2008 TV series Beethoven Virus created a sensation in Korea referred to as "Kang Mae Syndrome" and again earned him acclaim from critics and viewers.

[19][20] Kim received the Grand Prize (Daesang) at the MBC Drama Awards and his second Baeksang for Best Actor in television.

In late 2008, it was announced that his next project was a film about a character living with Lou Gehrig's disease, titled Closer to Heaven.

[4] In January 2011, Kim took on the role of Joseon's Sherlock Holmes in historical comedy-mystery film Detective K: Secret of the Virtuous Widow.

[32] The historical television series Six Flying Dragons followed, in which he played Jeong Do-jeon, who served as the first prime minister of the Joseon dynasty.