Arjun, whose father is producer Boney Kapoor, makes his debut in Ishaqzaade.
He told the Hindustan Times: "I worked on films like Kal Ho Naa Ho and Salaam-e-Ishq besides No Entry with my dad. Once, I happened to meet Salman bhai. Within seconds, he told me, 'I know you want to become an actor'.
"He said, 'Give it your best shot. Else, you will wake up as a 35-year-old and [might regret not trying your luck]. You might not lose all the 50 kilos'.
"When he said 'we' are going to lose weight, it gave me confidence that he is going to take me through this journey."
Producer Karan Johar recently described the film as "phenomenal", praising Arjun's "brilliant intensity".
Arjun has previously been romantically linked to Band Baaja Baaraat actress Anushka Sharma.
Watch a trailer for Ishaqzaade below: