For Naina Catherine Kapur (Preity Zinta), life is cold, grey and full. as it has been ever since a family tragedy shook her world.
between the constant bickering in her half Punjabi, half catholic household, her grandmothers temper, looking after her little sister and brother and helping her mother(Jaya Bachchan)deal with the family's financial troubles - Naina has no time for things like parties, fun or herself… she is twenty three, going on fifty. She is serious, she is boring.
Enter Aman Mathur (Shah Rukh Khan). Like a whiff of fresh air, he moves into their tiny Indian neighbourhood to take it over. Helping others resolve their problems, face life's little challenges, Aman has all the answers. Much to Naina's irritation, he insists on interfering in her life too...
Aman pushes Naina into doing things she would never dream of doing. He nags her till she learns to smile. He conspires with friend Rohit (Saif Ali Khan), and eligible manhattan bachelor to help find her happiness.
Kal ho naa ho is the story of Aman, Rohit and Naina's journey together. How they discover themselves, find the courage to love and come together to celebrate life.