Jawaani Jaaneman is a romantic comedy set in London about a middle-aged man (Saif Ali Khan) who is single and carefree and spends most of his time at parties with beautiful women. One fine day he suddenly meets a young girl who calls herself his daughter while she introduces him to her `hippie` mother (Tabu) with whom he had an affair many years back. Before he realizes what hit him he receives yet another shock when his daughter reveals that she`s pregnant! What does he do?