Johar, 43, was "genuinely moved" by the film, written and directed by M Manikandan.
"'Kaaka Muttai' is a gem of a film! Genuinely moved by it... Small film... With a huge heart! Congrats @foxstarhindi @dhanushkraja," Johar tweeted.
Jointly produced by Dhanush and Vetrimaaran, the comedy-drama features newcomers, Vignesh and Ramesh alongside Iyshwarya Rajesh and revolves around two slum children of Chennai whose desire is to taste a pizza.
The film premiered last year at the 39th Toronto International Film Festival, and released worldwide on last Friday.