Ayan Mukerji-directed "Yeh Jawaani Hai Deewani" has brought the real life ex-couple together on the screen after five years - their first and the last film together was 2008 movie "Bachna Ae Haseeno".
"I always expected from Deepika to reach very high levels, but I had no idea that she will become such a fine actress so soon. She is the first actress in front of whom I am a bit intimidated," said Ranbir, who himself has wowed people with variety in roles he played in films "Wake Up Sid", "Raajneeti", "Rockstar" and "Barfi!".
Talking about her growth in the industry, Ranbir said: "I felt like she was not doing what I expected her to do. That constant surprise was a good feeling. I know her so well. I know her advantages as well as disadvantages. She has turned her disadvantages into advantages. So, I am very happy for her."
Most celebrities are hounded by rumours and Ranbir accepts it as part of an actor's life.
"I can understand there is a demand for this. People want to know about their favourite actors and actresses - What they do? Who they can marry or not?
"But when it comes to you, you feel bad. But you have to focus on your work. Because when on Friday, your film releases, everyone forgets everything. It is part and parcel of the journey. You have to take it with a pinch of salt," said the 30-year-old.
Do you like to read about your contemporaries?
"We are curious... but we are all friends. We don't sit and bitch or gossip," he said and explained that "cold war" don't exist.
"I don't think there is any cold war. I am fond of all the actors of my generation - be it Ranveer Singh, Shahid Kapoor, Imran Khan, Varun Dhawan - all of us are busy with our work, we don't really meet much. But we try and catch up at award functions and parties," he said.
He admits there is competition, but a friendly one.
"There is a friendly, healthy competitive vibe going on. No one wants the other person to not do well. We get happy and jealous when we see a good performance, but we all congratulate each other and encourage each other. I guess it is too early in our careers to have this competition," Ranbir said.