In the movie, Jesse (Ethan Hawke) confesses to Celine (Julie Delpy) that he wrote a book about their meeting 9 years before, partially in the hope that she would read it and re-establish contact with him. Like Before Sunrise (1995), this is based on events in director Richard Linklater's own life. He had once spent a night walking and talking around Philadelphia with a woman called Amy in 1989. Though they initially stayed in touch over the telephone, they lost contact eventually. In 1994, Linklater shot Before Sunrise (1995), based on his night with Amy. Like Jesse in "Before Sunset", Linklater was secretly hoping that Amy had heard of the movie, and would show up at the premiere, but she did not. When "Before Sunset" was released, she did not show up either. It wasn't until 2010, before Linklater started production on the second sequel, Before Midnight (2013), that a friend of Amy, who knew about their story, contacted Linklater to tell him that Amy had died in a motorcycle accident on May 9, 1994, at the age of 24, a few weeks before he started shooting Before Sunrise (1995).
The man and woman that Celine speaks to in the courtyard of her apartment are played by Julie Delpy's real parents, Albert Delpy and Marie Pillet.
The longest take is about 11 minutes long.
Shooting took a mere 15 days.