Continuity mistake: Just after Timmy puts the goggles on and climbs into the back with Lex she says, "don't scare me" and turns to face him as he crawls into the boot. In the next shot she is immediately facing in completely the opposite direction, looking through the window. This is just before Timmy says, "oh cool, night vision". (00:58:35)
Continuity mistake: We see Dr. Grant helping Tim out of the car that has just fallen into the tree, then suddenly, they are about 5 feet under the car though the dialogue and split second cut suggest that they had merely just gotten out of the car and had not yet began their descent. (01:13:40)
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. (00:59:15)
Continuity mistake: When the group are at the velociraptor paddock Hammond says "And that's why we're taking extreme precautions". Dr. Malcolm's head changes from looking sideways to being tilted down a lot more. Also Hammond starts to turn and then turns again in the following shot. (00:31:50)
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 shot they have moved and are not at the end of the 4x4. They are back where they started, to the left of the wheel. (01:05:30)
Continuity mistake: When the tyrannosaurus is crushing the upside down Landcruiser and mud begins to flow in through the side shattered windows, Lex and Tim are already completely muddy all the way from the tops of their heads, possibly from previous takes.
Continuity mistake: When Muldoon and Hammond are talking about the tropical storm the first time we see a shot of Nedry's workstation behind them and there's hardly anything on the floor, but a few minutes later when Hammond says their lives are in Nedry's hands suddenly the floor is covered in trash.
Continuity mistake: When Ellie runs away from Muldoon towards the Power Station, she climbs over a tree and watches a path in front with two more fallen trees on the way. When she is about to jump over the first one some branches suddenly appear on the close-up to help her do the jump. Furthermore, when she is about jump over the second tree the close-up is a repetition of the previous tree.
Continuity mistake: When the T-rex is attacking the vehicle with the kids inside, Alan gets out of the other car. Even though it is pouring rain and Alan is standing perfectly still, no raindrops are seen hitting his solid, medium-colored shirt. It stays perfectly dry, even though there is nothing overhead that is shielding him from the rain. It is only after the scene cuts to him at the other car that the shirt is suddenly drenched. The rain is obviously CGI.
Continuity mistake: In the scene when Ellie is in the bunker trying to escape from the raptor, she stumbles along the floor gratings and is dragging her flashlight connected to an ankle bracelet. It appears securely connected as indicated by wildly bouncing and being flung around. She bashes her way through the door and slams it behind her, then she runs, suddenly free of the flashlight and connecting strap. If it was as securely attached as shown, she should have had a devastating fall when it was caught in the door, and the raptor would have won.
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.