The movie, co-produced by Fox Star Studios and Phantom Films, will see Karan in the role of a rich businessman who plays a crucial role in the life of Ranbir's character on screen.
`I think there is a beautiful actor hidden in Karan. I'm sure he'll make the character bigger than the actor," Vikas Bahl of Phantom Films said in a statement.
Karan was seen in "Dilwale Dulhania Le Jayenge", "Fashion" and "Luck By Chance". These days, he also seems to have brushed up on his dancing skills during his stint as judge of dance reality show "Jhalak Dikhhla Jaa".
`Karan is such a casting coup," said Vijay Singh, CEO, Fox Star Studios. "He is not only one of the most talented and versatile minds in the industry, he also has the ability to surprise. I believe he will do great justice to his role .`
"Bombay Velvet" will also see Ranbir and Anushka Sharma together for the first time. The duo will play lovers whose lives intermingle with the evolution of the city of 'Bombay', through the 50s to early 70s.
The movie will go on floors in July, and will release worldwide Dec 25, 2014. The first film of a trilogy, "Bombay Velvet" is the story of how a city became a metropolis, unfolding against the backdrop of love, greed, violence and jazz.