Manmadha Banam is a comedy romance movie in which, Ambujakshi (Trisha) is a successful film heroine. Madan (Madhavan) is a rich industrialist and he is the fiancee of Ambujakshi.
Madan starts suspecting Ambuja and their relationship is on the verge of break up. Ambuja goes to Europe on a vacation along with her childhood friend (Sangeeta). Madan hires a detective Bhushanam (Kamal Hassan) to track her movements as he is suspicious that she has a secret lover.