When Tom and his friend are looking in the window of the bridal shop, Tom sees his reflection in the window with the bridesmaid dress. In the window, Tom's arms and neck are bare. However, he is wearing a polo shirt with long sleeves.
When Hannah has just arrived back from Scotland, Tom decides to buy a very small bouquet of yellow flowers with netting. Then in the next scene, the flowers have changed and the netting is gone. Then in the next scene his flowers are the same as the scene before, but now the netting is back.
When Tom tries to get to Hannah's wedding, his car's license plate changes from shot to shot.
In the locker room, Tom is seated on a bench with shaving gel and deodorant next to him. In the first shot, the deodorant is laying on its side, to the right of the shaving gel. In the next shot, the deodorant is standing straight up, to the left of the shaving gel.
In one scene, the car behind Tom changes from a white police car to a yellow cab to a van.
In the beginning of the movie at the airport, several announcements identify the flight to London Heathrow as a British Airways flight. However, the check-in desks and 747 plane show the Virgin Atlantic logo, and the flight attendants on the plane wear the bright red Virgin Atlantic uniform.
When Colin and Tom are playing basketball, Colin appears to jump off a trampoline to make the slam dunk. He lifts his legs to jump, bounces, then jumps higher to reach the basket.
When Tom dials Hannah's Scotland number, he hits numbers as if he is dialing, but the screen just says "Hannah", with her number on it.
As the Range Rovers pull up to the summer castle when the bridesmaids first arrive in Scotland, they are not on the driveway. They drive off the lawn, possibly to help get a better angle on the shot.
In the locker room scene after the basketball game with Colin, as one of the men going into the shower removes his towel, the waistband of his boxer shorts is briefly visible.
In the opening party sequence, a logo sheet on Hannah's door shows various Cornell logos, including the redesigned crest logo, which wasn't used until 2004. In 1998, the official Cornell logo was the "Big Red Box", which was frequently criticized for looking like the J.C. Penney logo.
When Hannah chastises the store owner for having an alligator purse, the camera focuses on her and she says "You should be ashamed of yourself." The camera pulls back to follow Tom petting the dog. Hannah repeats her line, this time with no audio.
When Hannah is on a plane to Scotland, the announcement sounds like it came from an airport public loudspeaker. It should be a dampened sound from an overhead speaker.
When Tom and Hannah are on the streets walking to the home decor store (in preparation for the wedding) pedestrians who clearly congregated to watch filming can be seen, and one of them waves and points to the camera.
When Tom calls Hannah, it's 3:00 am in Scotland. With the 5-hour time difference, it should be 10:00 pm in New York, yet daylight is shining through Tom's window.
A few seconds after the the bridesmaids walk into the lobby through the revolving door, a double-decker bus passes on the street outside the double doors. There are no double-decker buses in New York.
The Kyle Rhea ferry goes from Isle of Skye to the Scottish mainland near Glenelg. The only other ways to the mainland are the Kyle bridge at Kyle of Lochalsh, or via the Mallaig ferry near Armadale, both days away by horse. Tom crosses in a few minutes overland on his horse, which is impossible without going for a swim.
Though the initial scene of the movie shows us how Tom and Hannah meet it is never truly explained how ten years after that meeting Tom and Hannah have become such good friends.
When Tom and all the bridesmaids arrive in Scotland and greet Collin and Hannah, Tom clearly kisses Hannah on the mouth, while they always kiss on the cheek.
Hannah says Colin needs permission to marry her because he is a duke. She talks to her minister at Grace Church, one of New York's historic Episcopal (Anglican) churches. If Colin is a Scottish Peer, he would be Presbyterian, and not allowed to marry in the Church of England.
Hannah, an art expert, pronounces Modigliani with a with a hard g. The g should be silent.