The actor appears alongside Ajay Devgn in the upcoming comedy, which sees him playing a conman determined to outsmart a rival trickster.
Dhawan previously worked with Dutt on the 1980 hit Taaqatwar.
He told New Kerala: "[Sanjay] is like an open book. He doesn't hide anything. I think he is basically the most simple guy I have ever seen.
"I started my career with him 20 years back as a director, and he is still the same. There is no change in him."
Dhawan said this week that he plans to cast good friends Dutt and Salman Khan for his next project after seeing them together on the set of Bigg Boss.
He said: "We all become the Rascals on the set. It was Salman and Sanju's first day of shooting for the show. Seeing their camaraderie I've decided to cast them together in a comedy."
Dutt will next be seen in Karan Johar's remake of 1990 film Agneepath, which co-stars Hrithik Roshan and Priyanka Chopra.
Watch the trailer for Agneepath below: