On the ferry, when the people gather at the stern to see the horse that fell overboard, a little girl next to Rachel screams, but the sound of the scream continues even after the girl stops and breaths in.
Near the end of the first scene between Noah and Rachel, Noah begins to eat an apple. He is clearly chewing while she is speaking but, without appearing to swallow, has an apple-free mouth when he replies. While Rachel speaks, he is once again chewing, without apparently having taken another bite.
When Noah is at the supermarket buying cigarettes, he pulls out of his pocket a bunch of junk such as coins, trash, and an old pack of cigarettes and dumps it on the counter. In the next shot of the counter, all the junk is gone except for a coin, and the old pack of cigarettes.
When Rachel is researching Anna Morgan and Moesko Island in the newspaper archives, she is unconsciously scribbling on a picture of Anna. Between shots, the scribble changes shape from fanning outward to completely vertical.
In the shot of the horse falling off the ferry, the ferry's name "Quinault Seattle WA" is seen on on the vessel's side. Rachel looks down at the horse in the water from the same place it jumped but the appearance of the ferry's name is now different, namely the position of the two words "Seattle" and "Quinault" are now flush with each other when they were not before.
After breaking into the records room, Noah is looking at Samara's pictures or photo negatives, holding them up to the light. The shot of him shows his fingers covering some of the first picture, but the next shot from his point of view the whole picture is visible and his fingers cannot be seen.
After watching the Samara medical video in the Morgan home, Rachel chases Richard Morgan to the stairs and the lighthouse illuminates a crew member's shadow on the wall. Richard is visible at the top of the stairs.
When Rachel is holding the tape at sunset just before watching it, the shadows and red light move across her and the room downward; however shadows cast by a setting sun would move upward not downward.
The counter numbers are messed up on both the original tape and the copy. This is not possible with a VHS tape - no such time code is recorded on the control track like Noah, who is a video expert, says. Additionally, Noah says that the control track can be used to tell what made the recording, also not true. The control track actually just tells the VCR how fast the tape should play and when to advance one second. There should be nothing wrong with this track - otherwise the tape wouldn't play and the VCR would just keep searching for the track and eventually eject the tape automatically.
As Rachel is driving to try to warn Noah, she has her cell phone in her right hand. In the next shot, she has both hands on the wheel. She actually drops the phone to take better control of the wheel to avoid traffic.
When Rachel picks up Katie's photos a monorail is seen above heading in the south direction, moments later another monorail passes going in the same direction on exactly the same track. This would not be possible as the first car would've had to return to the stop on the other end in Seattle Center, unload and reload passengers, before being able to make another trip south.
The level of the water in the well is not continuous. When Rachel is standing in the water it only comes slightly above her waist but if she were to fall from the height she did and the water was that shallow, she would have hit the bottom.
When Noah chops a hole in the floor with the axe, he removes a circle of wood approximately 4 feet in diameter. In the next shot, shot from below the floor looking up, the whole is easily over 15 feet wide.
When Rachel falls into the well, the torch light reaches the end of the well, meanwhile earlier on Noah says that they don't know how deep it is, as the light won't reach the bottom, and when they throw a rock into the well, it takes far too long to reach the bottom for how far Rachel falls into the water.
The death of Katie and all of her friends is listed as 10 p.m. However, 10 p.m. is the time it says on the clock when Katie's mother rings the house to check on the girls. Given the amount of time to takes Katie and her friend to go downstairs, answer the phone, Katie to talk to her mum, pour herself a drink from the fridge, discover the television that's turned itself on, turn it back off, go back into the kitchen, and then head back upstairs when she suspects that something's wrong, it definitely wouldn't have been ten o'clock anymore by the time she finally died.
When Rachel makes a copy of the tape, the images on the screen appear in a different sequence than when she originally watched it. The original sequence shows a chair sitting on the floor and then a ladder leaning against the wall. Later in the film, the chair is shown spinning upside down, and the ladder falls away from the wall. When Rachel records it, however, the chair is shown spinning in the air, and then the ladder is leaning steadily against the wall. With the supernatural involved, this is allowable.