When Vivian is offering Edward a choice of condoms, she is holding four colored condoms (other than the gold circle condom). In one shot, Vivian in holding the condoms in a certain order. In the next shot, they are in a different order and then in the third shot, they are back in the same order as in the first shot.
The pancake Vivian is eating was, for most of the scene, a croissant. Director Garry Marshall said he liked the performance she gave in the latter part of the scene better, so the croissant magically becomes a pancake, which she began to eat as they did more takes. While this may be the case, there is still a continuity issue. In the first scene with the pancake, she takes a second bite. In the next scene with the pancake in her hand, there is only one bite missing. Not only that, but the the pancake with one bite missing has a different bite pattern and is clearly a different pancake.
When Edward is sitting on the chair and Vivian on the stool she says to his answer 'business or pleasure' 'then that must make you a lawyer' if you look out of the patio doors it looks like they are on the ground floor as you can see hedges outside the door.
When Vivian finds Edward sleeping, she has a long white nightgown on when she comes in the room. She kisses him and they begin to make love. When Edward pulls her nightgown over her head, it is now a camisole.
When Edward drives up to Vivian's apartment at the end, she quickly pulls the ponytail holder off her hair and messes it up with her hand. But in the next shot, she is standing smiling and her hair is perfectly neat.
During the polo match Edward is shown wearing a straight-collar and the tie that Vivian gave to him as a gift, tied with a half-windsor. A later shot shows Edward with a spread-collar and that same tie, but with a full-windsor knot. As the scene progresses, the shot of Edward alternates back and forth between the straight and spread-collar (even with a shot of the spread-collar with a half-windsor knot).
Edward is wearing a vest when they leave the hotel, then in the limo on the way to the Blue Banana, the vest is gone, and then when he confronts the thugs in the alley, he's wearing it again (Garry Marshall said it kept bunching up in the limo scene, so he took it out).
When Vivian and Edward are in the penthouse and Edwards gives Vivian $100, she puts the money down in her boot. After the champagne is delivered to the hotel suite she takes off her boots and the money is nowhere to be seen.
When Philip Stuckey tells Vivian that "this is not a home, this is a hotel room and you're not the little woman," the champagne glass Stuckey holds goes from his right hand to his left hand in between shots as he sits on the couch next to Vivian.
When Vivian is being shown table etiquette by Barney, the Hotel manager. The camera pulls back as if it's on the end of a long boom rather than a dolly. You can tell it's a long boom because of all the up and down shaking which gets worse and worse.
The goof items below may give away important plot points.
At the very beginning of the film, Vivian's right hand can be seen using a black Magic Marker to color in the scuff marks on her boots, however both Vivian and Julia Roberts are left-handed, as can be seen at the end of the film when Vivian is writing in a notepad when Phil arrives.
In the last scene when he "rescues" her on the fire escape, camera shots from her window show the ground as being dry even though it has been raining. Shots from the ground looking up at the fire escape show the ground as wet.