Audio/visual unsynchronized: When Naina returns home from Central Park, her lips say, "St Paul's Cathedral."
Revealing mistakes: During the title song, "Kal Ho Naa Ho," at the scene where Aman and Naina are dancing in the night, after Aman touches Naina with the rose, it shows him throw the rose behind him, and at the end of the embrace the rose reappears in his hand.
Audio/visual unsynchronized: In the start of the song "It's the Time to Disco" the sound of a zipper being opened is heard much before Preity Zinta actually opens the zipper of the jacket.
Crew or equipment visible: In the scene where Aman Mathur enters the kitchen to look for Rohit Patel, who has gone for a date with Camilla, he and Kanta Bhen have a conversation in the kitchen, in front of the glass door. The reflection of the boom mike is visible on the glass door.
Errors in geography: Throughout the film, shots of New York are interposed with similar shots of Toronto. The film tries to make the viewer believe that the Toronto shots are, in fact, New York, but the architectural styles and obvious Toronto landmarks are completely different than those found in New York.