Bewafaa is a film that tells the story of changing morals and values in a fast changing world.
Anjali (Kareena Kapoor) is the younger daughter of her Canadian mother (Nafisa Ali) and her Indian father (Kabir Bedi) living in the city of Montreal, Quebec. She shares a hale and hearty relationship with her parents but has a secret to hide. And she reveals this secret only to her elder sister Aarti (Sushmita Sen).
The secret is her love for a budding musician Raja (Akshay Kumar). Raja is not a rich man but that does not deter Anjali from loving him. Aarti assures Anjali and Raja that she will convince her parents of their true love.
But unfortunately fate has different plans for them. Aarti passes away on the birth of her twin babies. Circumstances force Anjali to marry Aarti's husband, Aditya Sahai (Anil Kapoor). With the much older and mature Aditya Sahai, Anjali migrates to New Delhi.
Aditya is a business tycoon who hardly finds any time for his sister-in-law turned wife Anjali or his two lovable daughters from Aarti. Anjali fulfills every role asked for her by the society but cannot bridge the gap between herself and Aditya. She finds herself in a marriage that has no compatibility but only compromise. Her only source of solace are her two endearing stepdaughters.
Amidst all this, one fine day Raja who is now a famous fusion singer walks back into her life. Suddenly Anjali is torn between two men - her indifferent husband and her ex-lover. By the time Aditya wakes up to reality, Anjali has embarked on to an extra-marital affair with Raja. And thereby she is tagged as a Bewafaa - The Unfaithful.
How Anjali negotiates her relationship with Aditya and Raja as also Dil (Manoj Bajpai) and Pallavi (Shamita Shetty) who are Aditya's close friends and confidantes forms the basis of the second act of Bewafaa.