JAWAANI JAANEMAN is the story of a 40-year-old playboy whose life suddenly turns upside down. Jassi aka Jazz (Saif Ali Khan) is in his 40s and is based in London. He's single and in no mood to commit. By profession, he's a real estate broker and works with his brother Dimpu (Kumud Mishra). But he spends most of his time partying and getting involved with girls. He is also about to seal a redevelopment deal that will make him the biggest broker in London. Life is going great for him until one day he meets Tiya (Alaya F). At first he flirts with her, with the ultimate aim to take her to bed. However, she drops the bomb that she might be his daughter! To make matters worse, the DNA test confirms that they are related. And that's not all. It also comes to light that Tiya is pregnant! So Jazz finds out that he's not just someone's father but also to-be grandfather! What happens next forms the rest of the film.