Rai-Bachchan will take on the role of a major Bollywood actress, who gets charmed by a cricketer played by the Aisha star, Mumbai Mirror reports.
Singh told the tabloid: "Yes, I am doing the film and I am over the moon. I can't speak anything about the character but it feels great to be acting opposite Aishwarya Rai."
However, he added that the actress's part in the film would not stop him approaching it like "any other film".
Director Madhur Bhandakar had reportedly been considering Rai-Bachchan's husband Abhishek Bachchan for the leading man.
Singh made his debut with Sikander, denying rumours that he had been cast because of his prominent family background.