Revealing mistake: When Grant tells Lex and Tim about the breeding he then gestures to the dinosaurs' footprints. Some of the footprints are very square in shape and have obviously been stamped in the ground.
Continuity mistake: When Tim is up the fence Grant starts counting for him. When he starts to count, Lex and him are next to the fence. In the next shot, Lex and him are much further away from the fence.
Continuity mistake: When Hammond watches the vehicles leaving the visitor center the first car is passed the main steps. In the next shot of the car, they are just moving past the steps.
Continuity mistake: In the opening scene Jophery is being attacked by the dinosaur in the cage and Muldoon is holding onto him while the workers shock the dinosaur. Muldoon's hat is on in one shot, then the camera cuts and it is off while the camera is dollying forward, then it is on again. This happens just as he is about to shout "SHOOT HER! SHOOT HER!"
Continuity mistake: The T-rex completely destroys the outdoor bathroom facility that the lawyer ran into. The lawyer is perched atop the toilet and the remaining damaged wall behind him is tilted backwards. When the camera cuts to a shot where the lawyer is seen from behind and the T-rex is just about to eat him, the wall is missing. When it cuts back to a front shot, the wall is back again.
Continuity mistake: When Grant shoots at the window in the control room, and we see the holes, they are holes from rifle bullets. But the shell casings on the floor is from a shotgun. And yes - shotgun shells do exist with one big slug in them, but then the holes in the glass would be a lot bigger.
Continuity mistake: After Nedry has sprayed the shaving cream on his hands, (and after placing it on the pie) we see a sideview shot where he lowers his hands to his sides. The shot changes to the front and his hands are up again, drying his hands off with a napkin. It was too fast to move his hands.
Continuity mistake: In the scene from behind Dr. Grant we can see the cow being lifted straight up. You can see that the cow is rather close to Dr. Grant. Then the scene cuts and the cow is already in the middle of the top of the Velociraptor paddock. Judging from the distance between Dr. Grant and the paddock from the previous wide-shot, and the fact that Dr. Grant made no big moves, the crane couldn't pass that distance between the two shots.
Continuity mistake: As the T-Rex is looking for Lex and Dr. Grant, Dr. Grant says "Don't move. He can't see us if you don't move." When he says this he is to the left of the wheel arch. Then, the T-Rex blows the hat off Dr. Grant who, with Lex is at the end of the upturned 4x4 when the T-Rex knocks it but in the next scene they have moved and are not at the end of the 4x4. They are back where they started, to the left of the wheel.
Continuity mistake: At the start of the Badlands sequence, the palaeontologists are brushing-out a dinosaur skeleton. In the close-up shot, they are working on the head (someone 'picks its nose') and one of them has a red-handled brush. When we cut to a wide shot, there is only one person working on the head (the nose is still being brushed) and there is no red-handled brush in sight.
Continuity mistake: When Dr. Grant is scaring the kid with his Raptor claw, the pouches on his belt holding his knife and things move around.
Visible crew/equipment: When the two Explorers start off on the tour of the island and the vehicles reach the Dilophosaur exhibit, there is a shot of Lex, Tim and Gennaro, looking out their Explorer's passenger-side windows. Right above their heads, fastened directly above each window, are wind-screen covered microphones. Obviously placed there to pick up actor dialog, neither of these particular mikes are seen again before or after this shot.
Continuity mistake: When Timmy hears the T-Rex stomping and takes off the night vision goggles, his hair in back comes up. In the next shot, his hair is down again.
Continuity mistake: At the end of the scene with the sick Triceratops, just after Dr. Harding says, "I'm in a gas powered jeep", Dr. Malcolm's hands move from on his hips to on his chest, whilst Dr. Grant's hands move from behind his back to in front of him in the next shot. [These don't seem to be consecutive shots; Laura's hands are moved, Sam's hands are moved, Jeff's hands are moved and "Lexi" is in a completely different position.]