Produced by Balaji Motion Pictures, the film features her as Mumtaz. She will be seen on the big screen after a gap of 10 years when the film releases Aug 15.
Sonali's last big screen outing was again a guest appearance in Shah Rukh Khan, Priety Zinta and Saif Ali Khan starrer "Kal Ho Naa Ho", in which she had played a doctor.
"The film is directed by Milan Lutharia and I have known him since a long time. He used to assist (Mahesh) Bhatt sahab and my first ever song 'Sambhala hai maine...' was shot by Milan. So the equation and the relationship go very far back," Sonali, who is married to Goldie Behl, told IANS.
"Once Upon A Time In Mumbaai Dobara" stars Akshay Kumar, Imran Khan, Sonakshi Sinha in the main leads.
Another reason for Sonali to give a nod to "Once Upon A Time In Mumbaai Dobara" was its producer Shobha Kapoor, who is a good friend of her mother-in-law.
"Shobha aunty has been friends with my mother-in-law for the past 40 years. So, when she calls her and asks for me to do something, I can't say no to her. So it's just that," said the actress known for films like "Sarfarosh" and "Zakhm".
"I have not charged them for anything. So it's not a professional kind of a thing for me, it's just a guest appearance that I am doing for the people that are involved in it. It's a very interesting literal role," added the 38-year-old who is happily married, has a son and enjoys spending time with him.