The film's leading child artists -- J Vignesh and Ramesh -- bagged the honour for their poignant portrayal of inseparable siblings living in a slum.
Released last September, "Kaaka Muttai", which shared the best children's film honour with Marathi drama "Elizabeth Ekadashi", was produced by Dhanush's Wunderbar Films and Grass Root Film Company.
"Wunderbar films and grass root film company's kaakkamuttai wins 2 national awards. Best child actors and best children film. We are really proud as producers of kaakkamuttai," Dhanush tweeted.
"My sincere thanks to Manikandan the director and the 2 little gems the stars of the film," he added.
"Kaaka Muttai" is a heart-wrenching tale of the two brothers who are unaware of their deprived status and have a confrontation with the tastelessness of globalisation.