Factual error: The locomotive in Ponyboy's dream of his parents' death in 1965 is a Burlington Northern C30-7. Burlington Northern did not begin operations until 1970 and the C30-7 was not built until 1967. In the same scene, the locomotive's stripes and cab numbers are mirrored.
Plot hole: The pictures used in the newspaper article regarding the fire are obviously taken after Ponyboy and Johnny ran away since Pony's hair is blond and Johnny's is short (their hair was cut and dyed after they ran, ruling out the photos being old school photos), yet Johnny's face is free of burns. This would mean the pictures were taken while they were hiding in the church, which would be impossible.
Continuity mistake: When everyone is at the movies and Cherry throws her soda in Dally's face, he's dripping wet; you can see him blinking soda out of his eyes. A few lines of dialogue later, his face is completely dry, even though he didn't wipe it off with anything. It couldn't have dried so fast.
Continuity mistake: In the drive-in scene where Ponyboy and Cherry get up to get popcorn and soda, Ponyboy leaves with the popcorn Dallas gave him. They both purchase more popcorn and soda in the snack bar yet when they return to their seats, Ponyboy only has the popcorn he left with and Cherry has nothing.
Continuity mistake: When Ponyboy and Randy are talking, the camera keeps switching back to Two-bit making fun of the other Socs. When it does this you can see Ponyboy and Randy in the background. If you look carefully at Randy his arms are resting down the side of the car, but when the camera goes back to him as a close up his arms are resting on the roof of the car. This happens several times.
Factual error: The story is set in 1965, yet it shows many modern (as of filming in 1983) pieces of medical equipment, such as disposable plastic nasal cannula, modern plastic IV tubing and cut offs, etc. Also most hospitals in the 1960s still had open wards with many patients cordoned off by curtains, instead of private rooms as depicted in the movie.
Continuity mistake: In the church when Ponyboy is reading Sodapop's letter, Dally is in the background with his left hand on his leg. When the shot switches to Dally, his hand is not on his leg, and he is lighting a cigarette. When the shot switches back to Ponyboy, Dally's hand is back on his leg.
Continuity mistake: In the scene where Two-Bit and Ponyboy are visiting Dally in the hospital, when Dally asks Two-Bit for his switchblade, he extends his right arm back for it, and his left arm is under the sheets. In the next shot, his left arm is extended backwards, even though there was no time to switch arms.