Continuity: When Nancy checks her watch she is wearing a short-sleeved nightgown, but the closeup shows a wrist with the end of a long blue sleeve on it.
Continuity: The part in Nancy's hair swaps sides When her father is talking to get about Tina.
Revealing mistakes: Crash mat visible when Freddy falls over the banister.
Revealing mistakes: When Nancy falls out the window of her house, a crash mat can clearly be seen from behind the bush when she lands.
Continuity: In final scene, the girls singing "One, two, Freddy's coming for you" change places between shots.
Continuity: The person who gets up to speak in the classroom is not the same person who was sitting in the same seat in the establishing shot a few seconds earlier.
Revealing mistakes: Crash mat visible when Nancy jumps out of the boiler room and lands in her lawn.
Revealing mistakes: In the beginning when a character is killed by Freddy, you can see their fake chest lifting when they are moving around.
Continuity: When Freddy is knocked off the stairs one of the razor blades from his fingers has broken off. Yet in the next scene, the blade is back on his finger.
Continuity: When Nancy sneaks Glen back out the bedroom window after she wakes up, the lights are turned off in her bedroom. However, when it shows the house from outside, her bedroom lights are turned on.
Revealing mistakes: When the sheet is coming around Rod's neck to choke him you can see the wire that is pulling it.
Continuity: Throughout the movie, along with all the sequels, Freddy's "razor" glove is on his right hand. When Freddy is chasing Tina, there is a quick shot of him jumping out from behind a small tree and his glove is on his left hand.
Continuity: In a wide shot, when the bars have just been put on the house, the front door window bars are different than the close-up of Nancy on her porch. The closer shot shows a heart shaped design rather than the three-bar pattern of the wide shot.
Revealing mistakes: When Nancy runs up the stairs near the end of the movie, the camera shows a close up of her feet sinking into the "goo" stairs. You can see exactly where she going to put her feet as the "goo" pots are clearly visible.
Revealing mistakes: Obvious stunt double for Nancy when she is pulled underwater. The double also has blonde hair. (In the audio commentary actress Heather Langenkamp is watching this scene, and she embarrassingly says, "That is not me!")
Continuity: To wake herself up, Nancy smashes the outside of her arm against the boiler. But when she wakes up, the burn mark is on the inside of her wrist.
Continuity: Before Nancy goes to sleep, when Glen is suppose to be watching her, her blue phone is on the left-hand side, next to the chair. When Nancy wakes up screaming, it's on the right.
Audio/visual unsynchronized: When Freddy is on fire in the basement we hear him scream, but his mouth is closed.
Revealing mistakes: When Freddy is on fire you can see the fire protective mask he's wearing.
Revealing mistakes: Freddy intimidates Tina by slitting off his own pinkie and ring fingers, but blood only spurts from the pinkie.
Continuity: During her nightmare in the dream clinic, Nancy pulls Freddy's hat out of her dream and into reality. Later during Nancy's final nightmare, Freddy grabs her suddenly, and for that one brief shot is wearing his hat, then he remains hatless for the rest of the film.
Continuity: When Tina is killed, her shirt is ripped open and her chest is cut by Freddy's four blades. In the next shot she is pulled up the wall then onto the ceiling and her shirt is buttoned up.
Continuity: When Nancy sets the booby traps for Freddy, the "explosive lamp" she prepared is different when it actually explodes.
Revealing mistakes: Nancy's gray streak switches sides between the two movies.
Revealing mistakes: Obvious stunt dummy used when Nancy's mother is pulled through the window in the door at the end.
Audio/visual unsynchronized: When Nancy wakes up from her nightmare in the clinic, a female voice says "This will help you sleep" and neither Nancys mom or the nurse's mouths are moving.
Continuity: When Nancy is by the bush with Rod, his hand and chest are covered with blood, but when he runs out and is surrounded by the police, what is supposed to be moments later, his chest is clean.
Revealing mistakes: When Freddy is on fire it is obvious it is a stunt double in a fire proof Freddy suit.
Continuity: The size of the pimple on Nancy's forehead changes from scene to scene.
Revealing mistakes: While Freddy is chasing Nancy down the stairs after the sledgehammer hits him, he falls down form the top of the stairs. When he falls, you can clearly see Freddy land on a bed to break his fall.
Continuity: Towards the end of the movie, Nancy was about to go home and go to sleep so she could bring Freddy back with her. She told her dad to come break down the door in exactly 20 minutes so he could get Freddy. In the 20 minutes before she was scheduled to wake up from her dreams, she was able to string up all those booby traps and have a heartwarming talk with her mother and then proceed to fall asleep to go get Freddy. That seems highly impossible.
Revealing mistakes: In the full-screen version of ‘A Nightmare On Elm Street’, during the first nightmare sequence, right before Freddy pops up to scare Tina you can see Robert Englund as Freddy crouched down and moving into place behind her.
Revealing mistakes: After bringing Freddy into the real world, Nancy runs down to the front door and breaks the window. You can already see the cracks in the window that were probably made so it would break easier.
Continuity: When Glen is just about to be killed, we hear the radio announcer saying that "it's twelve midnight". But when he is being dragged into the bed by Freddy, the clock beside his bed shows 11:52.
Continuity: When Glen's parents come inside the house they leave the front door wide open. After Glen's father hangs up the phone on Nancy, the parents go upstairs without shutting the door.
Continuity: In the promotional poster you can see Freddy's glove is left handed above Nancy, his left thumb can be clearly seen. He is actually meant to be right handed.
Continuity: When Glen is watching over Nancy while she sleeps, the lamp is turned off, darkening the entire room. When she wakes up from her nightmare, her bedroom light is turned on, lighting the entire room.
Crew or equipment visible: When Nancy and her mother take off with the car after talking to Nancy's father in Rod's funeral, you can see the camera man, the boom microphone, and the whole film crew reflected in the back of the car.
Continuity: When Nancy is in the bath the position of the blue bath pillow changes from quite high behind her head and her arms on her chest to the pillow very low and her arms on her tummy.
Continuity: when Nancy rips the phone out the wall and wraps it up she places it on the bed. The position of the phone, pillow and phone cable change after she opens her bedroom door.
Continuity: When Nancy's mum disappears into the bed near the end of the film it is clear that the pillows change position and size. They go higher up the bed.
Errors made by characters (possibly deliberate errors by the filmmakers): When Nancy encounters Freddy in the boiler room and he slices his abdomen open, his body is not burned or scarred. This is highly unlikely, since he was supposed to have been burned to death.