Continuity mistake: Just before the Tyrannosaurus Rex escapes from its pen, it drops a goat's leg on Lex and Timmy's car. When it comes back to attack them, the leg is gone.
Visible crew/equipment: Watch carefully the scene where the raptors enter the kitchen (that angle where you can see almost the whole kitchen while raptors are coming in from the far away door). As the first raptor enters the kitchen, you can see someone grabbing its tail to hold the puppet-thing steady.
Continuity mistake: Take note when the vehicle starts chasing Sam Neill and the kid down the tree. When it first starts to fall, it smashes a headlight and damages a foglight. In the next shot both lights are undamaged and operational.
Continuity mistake: Where Alan and the kids are about to climb the fence, when he throws a stick at the fence, his hair is messed up, it is sunny and windy. In the next scene his hair is combed, it is shady, and it is not windy.
Continuity mistake: When Lex and Tim are in the car and the T-rex is attacking them, at one point the T-rex smashes through the roof of the car and the clear roof falls through on top of Lex and Tim. The T-rex breaks it with her teeth, but in the next shot it's whole again.
Continuity mistake: When the lawyer jumps out of the Explorer (just before the T-Rex approaches) he leaves the Explorer door open. In the next two shots the jeep door is closed, but when the T-Rex shows up, the boy moves to the door and closes it.
Continuity mistake: When the T-Rex has a raptor in its mouth at the end, the raptor disappears completely from the T-Rex's mouth for one frame. It's just after it's picked up - the T-Rex swings it left, then right, and as it swings to its left again the raptor disappears. If you want to be even more precise, there's a slatted/stepped white bit above the door - the raptor disappears about 3 frames after its foot moves above that white bit.
Continuity mistake: When the tour trucks are stopped outside the Tyrannosaurus Rex paddock, we are shown a goat in a cage (inside the paddock) that appears to be at the same level as the road (outside). However, when Dr. Grant and Lex go over the wall, the ground is several stories down. This is because the ground along the paddock side of the fence is not level. The tour cars are brought alongside the top of a hill in the T-Rex paddock.
Revealing mistake: A live bull is lowered in a sling to feed the raptors in the pen, but when the shredded sling is brought back up, there's no blood on it. How could they have shredded the sling without drawing blood on the bull?
Visible crew/equipment: In the opening scene, a velociraptor is being introduced into the park from a shipping container. The velociraptor runs into the gate as it opens, knocking Jophery off the top; he falls to the ground and is attacked. As he falls, two hands come in to break his fall and prevent him from hitting the camera.
Continuity mistake: When the baby dinosaur is born, one minute the robotic hand is there behind the egg as it's hatching, then in the reverse angle the hand's suddenly disappeared.
Continuity mistake: After Ellie injures her foot running from the raptor, her limp switches legs repeatedly for the rest of the film.
Continuity mistake: When the helicopter first lands on the island it is clearly not on the cross on the landing pad. Later in the scene it is.
Character mistake: The correct spelling of stegosaurus is steg"o"saurus yet when Nedry steals the embryos, the freezer says steg"a"saurus.
Continuity mistake: The satchel of money Nedry receives as a down payment for getting the embryos off the island vanishes from his arms as he looks at the false container of shaving cream. It vanishes mid-sentence; he had no time to put it down.
Continuity mistake: In an early scene, Samuel L Jackson's character is struggling to get the computers up, and he is smoking away. A full cigarette, then half, then full, all without lighting a new smoke.
Factual error: When the doctor is showing off the piece of amber that they have gotten the DNA from, there is a problem. The mosquito in the amber is a male, as one can tell by the antennae. Because it is only the female mosquito that feeds on blood, the male should only have nectar in its stomach. To make it worse, in that species of mosquito, Toxirhynchites, both the males AND females are flower feeders, and would therefore have no blood, or dinosaur DNA in their stomachs.
Continuity mistake: At the badlands, when Hammond's chopper has landed and Grant goes to the trailer to open the door, if you watch the hinges of the door, they're on one side then it cuts to the inside of the trailer and the hinges are on the other side.
Revealing mistake: When Nedry is attacked by the Dilophosaurus, (the spitting dinosaur), the first spit supposedly lands on his shirt, BUT if you look closely, Nedry slaps it there himself with his hand - there's only a little bit on his shirt before he hits himself, then there's loads.