Continuity mistake: When Marlon stocks the vending machine, the camera (inside the back of the machine) shows him stocking the 1st row with brown-wrapper candy bars. He starts stocking the 2nd row with yellow-wrapper bars; Truman interrupts him for a minute (during which Marlon doesn't touch the bars at all). When Marlon continues, the yellow bars have changed to something darker (it's not just a different camera view; even barcodes are different). After another brief interruption, Marlon continues again, and the yellow bars are back. (00:35:00)
Continuity mistake: When Truman is going mental, with his wife in his car and they are about to go around the circle loads of times, it shows a shot of the car from the back. If you look at his wife's seatbelt it is on. However, a couple of seconds later it has another rear shot of the car and you can see the wife putting on her seatbelt again, when she already had it on. (00:48:00)
Continuity mistake: In the scene where Truman is on the boat, it shows a shot of him wearing a green shirt and black trousers but in the next shot he is wearing a blue shirt and khaki trousers.
Continuity mistake: When the fallen lamp has settled, the glass and parts of the housing are in the sunlight, and the light is in the shadow, with the camera looking into the side of the shadow. As Truman comes out to investigate, the light has been turned to a new direction, the pieces of the housing are missing, and the glass is splayed out a lot more than it originally was.
Continuity mistake: At the end, when Truman is supposedly looking into the sun, there is a shadow on one side of his face, indicating that the light source for that shot is to his side. (01:32:15)