John Cusack and Kate Beckinsale filmed only a few days together during the shoot, much like their characters saw each other only for a limited time.
The drink Sara and Jonathan have at Serendipity 3 is its famous Frozen Hot Chocolate. Also, since the movie opened, the table where they sit has been called the Star Table at the restaurant.
During filming of this movie in NYC, the following note was posted on a production trailer: "Yes, we are filming a movie. It is called 'Serendipity'. It stars John Cusack and some girl from Britain that you wouldn't know - even if we told you her name. We will be shooting tonight until midmorning. Please don't ask the crew any questions. Even if they don't look like they are working, they are thinking."
Kate Beckinsale and Molly Shannon disagreed with using stunt doubles and performed their own stunts.
The book "Love in the Time of Cholera" is mentioned in another John Cusack movie High Fidelity (2020).