A rising star early in her career, she gained acting awards for Han Jae-rim's relationship drama Rules of Dating (2005), and Park Kwang-hyun's Korean War comedy Welcome to Dongmakgol (2005).

Following roles as a developmentally disabled daughter in Herb (2007), a suicidal woman in Kill Me (2009), as well as her marriage to Tablo in 2009, Kang began starring in more conventional melodramas in TV and film such as Girlfriends (2009), Miss Ripley (2011), The Wedding Scheme (2012), Lucid Dream (2017) and Jugglers (2017–2018).

Her portrayal of the character Mi-do won her considerable attention both domestically and abroad, and she also picked up acting honors from the Grand Bell Awards and Pusan Film Critics Association.

The sharp-edged relationship drama Rules of Dating, in which she starred opposite Park Hae-il, proved to be an unexpected hit, and then two months later she took a small but central role in box office megahit Welcome to Dongmakgol.

[2][8][9] After playing the developmentally disabled daughter to veteran actress Bae Jong-ok in the 2007 melodrama Herb,[10] in 2009 Kang starred in two unconventional romantic comedies with roles she imbued with her trademark quirkiness.

[19] After making the little-seen 2007 KBS drama Flowers for My Life with Cha Tae-hyun, Kang returned to television in 2011 in MBC's Miss Ripley, a tale of one woman (Lee Da-hae) who spins a web of love, ambition and lies.

[26] Shot over a one-year period between October 2008 through November 2009,[27] the US-Korea co-production premiered at the 2011 Los Angeles Asian Pacific Film Festival[28] and received the Independent Feature Filmmakers Award at the 2011 Cine Gear Expo.

[29] Kang was next seen in rom-com cable TV series The Wedding Scheme, about a kimchi factory president so determined to marry off her four daughters that she embarks on a grand marriage project by getting her girls to cohabitate with prospective groom candidates.