Dr. Kkang is about a lazy bum who disguises himself as a doctor to get a job, and while under disguise falls in love with a female doctor.

Kang Dal Go is a middle leader of a gang who gets investigated by the police for some incident and gets kicked out of the gang. So he moves to Seoul from Busan and disguises himself as a fake doctor. While acting as a fake doctor he meets Kim Yoo Na, a real doctor. Suk Hee Jung grew up as an illegitimate child but he studies and works very hard to become a successful prosecutor. Lee Hye Young, whose husband was killed by gangsters, is Yoo Na's classmate and sister-in-law, and is raising her son alone. The drama shows the story of Dal Go and Yoo Na's unbalanced love, with Hee Jung forming the third party in their love triangle.