Continuity mistake: When Joe is on the yacht talking to his father, Joe is mixing up martinis, pours them, and adds an olive to one, and then an olive to the other. The camera cuts away to his father and then cuts back and now the second martini has no olive, so Joe adds an olive again.
Continuity mistake: In the dinner party scene where Meg discovers who Tom really is, they are seen walking around a buffet table filling their plates with food. The food on Tom's plate changes in quantity and placement of items on the plate from scene to scene.
Continuity mistake: Tom hands the little girl a red ring to toss on the bottles and you see a green one land (different colour ring leaves her hand and lands on the bottle). The rings keep changing colour throughout the scene.
Continuity mistake: When Joe goes to Kathleen's house when she's sick, there are used Kleenexes in front of the box on the right side of the table and the fruit basket. Joe is in the kitchen making tea, but when he comes into the room, it shows the table again and the Kleenexes are gone. The runner on the table is also suddenly bunched up, despite no-one going near it.
Continuity mistake: After Kathleen (Meg Ryan) and Joe (Tom Hanks) talked about what it would have been like if they hadn't been enemies in the book business, Kathleen says she has to go and heads off to her apartment. During this time, the camera switches back and forth between Joe and Kathleen. Kathleen's right sweater sleeve cuff is by her wrist in one shot and rolled up by her elbow in the next. In the next shot it goes back down again.
Continuity mistake: In one of the early scenes where Joe Fox and his girlfriend are having breakfast, Joe's orange juice carton moves around the table by itself. Joe's glass seems to refill itself in an instance without any juice leaving the carton and when Patricia throws a newspaper on the table, Joe is holding his glass in his right hand; in the next shot it's in his left. At one point Joe puts the glass down on the table and in the next shot picks it up from the top of his newspaper.
Continuity mistake: When Tom Hanks is agitated over how to explain his absence at the Cafe Lola, he paces back and forth while looking at his computer. When there is a close-up shot of the computer, we see his chair is right in front of it. But when he returns to sit down, the chair is way off to the side of the screen.