A Gentleman is about a simple, innocent guy in Miami whose life turns upside down due to a supposed case of a mistaken identity. Gaurav (Sidharth Malhotra) is doing well in his career and his quite stable financially. He is attracted to Kavya (Jacqueline Fernandez) but she finds him too boring. On the other hand, Rishi (Sidharth Malhotra) is a sexy, risk-taker gangster on the run. He has got into the bad books of the evil Colonel Vijay Saxena (Suniel Shetty) who's trying to hunt him down. What happens next and are Rishi and Gaurav the same person or are they different is something that forms the rest of the film.