(2005), Capital Scandal (2007), Hong Gil-dong (2008), Lie to Me (2011), Incarnation of Money (2013), Big Man (2014) and Children of a Lesser God (2018) as well as the films Rough Cut (2008) and My Girlfriend Is an Agent (2009).

From 2003 to 2004, using the stage name Kang Ji-hwan, he began appearing in small roles on television, which included the sitcom Nonstop 4 and the Korean dramas Summer Scent and Save the Last Dance for Me.

Kang shot to fame in 2005 with Be Strong, Geum-soon!, in his first onscreen leading role as a fastidious doctor who falls for a widowed hairdresser (played by Han Hye-jin).

Kang then reunited with previous leading lady Kim Ha-neul in My Girlfriend Is an Agent, a 2009 action-romantic comedy in which their characters are former lovers and spies trying to conceal their professions from each other.

[19][20] The 2012 comedy film Runway Cop reunited him with previous costar Sung Yu-ri (from Hong Gil-dong) and director Shin Tae-ra (from My Girlfriend Is an Agent).

[29][30] Then in 2014's Big Man, he played a "good-for-nothing" orphan who is tricked into thinking that he is the long-lost eldest son of a wealthy tycoon's family, when they only want to harvest his heart for a transplant.

[31][32][33][34][35][36] Kang and Yoon Jin-seo shot the gangster love story Heartbreak Hotel in Los Angeles and Las Vegas, and the indie was released in 2015.

[37] He was next cast in the Korean-Chinese romantic comedy A-lister Fall from the Sky, about a scandal-ridden Hallyu star who goes to China and encounters his biggest fan (played by Jiang Yuan).

[44][45] In 2019, Kang starred in the series Joseon Survival Period, but due to sexual assault allegations against him, he was replaced by Seo Ji-seok from episode 11 onward.

[52][53] In 2012, S-Plus Entertainment moved to extend Kang's contract with them for an additional eight months, citing his lack of projects for that same length of time due to CEMA's edict.