Kanni Maadam narrates the tale of a Madurai-based couple who runs for their life to Chennai as the relatives of the boy are quite enraged by their act. When both of them start a new life slowly and steadily, a tragedy hits them in the form of a road accident. Malar (Saya Devi) takes quite some time to come to terms with Kathir's (Vishnu) demise, but struggles hard to come up in life when she realizes that she is going to be a mother. Two auto rickshaw drivers, who live nearby her home, come he her rescue (Sreeram and Murugadoss). How she faces various challenges from different quarters form the rest of the story.