The 47-year-old actor is all set to star in contemporary romcom, also produced by Ranjan, after a spell of action films and out-and-out comedies.
The actor will be seen in an all-new avatar that will resonate with today's youth.
Talking about Devgn's character, Ranjan said in a statement, "The way I see it, it's the side of Ajay that comes most naturally to him. His uber-cool personality in real life has seldom been explored. There is a subtlety in his humour that blends perfectly with my writing."
Ali and Devgn have previously worked in "Once Upon a Time in Mumbaai" (2010).
Devgn was last seen in "Shivaay", which was also directed by the actor.