Continuity mistake: When the school bus is leaving Pacific Tech, the name "Southridge" is painted directly on the front of the bus. When Dr. Forrester finds the wrecked vehicles in the city later in the film, the name "Southridge" is now painted on a separate wooden sign that he picks up.
Continuity mistake: When Dr. Forrester and Sylvia are eating in the farm house, as Forrester sits down he reaches for Sylvia's cup then commences to pour coffee in it. Yet in the following shot he no longer is holding the cup, and the cup has jumped back to its original place on the table.
Continuity mistake: Look closely when the Martian "spaceships" make their first appearance, underneath are three electro-magnetic legs supporting it meaning they walk rather than fly, much like the tripod war machines in the original book, yet after this scene they can't be seen again. The studio opted to forgo the use of this special effect after this particular shot. (This is best seen on the DVD version of the film.)
Continuity mistake: The tri-lens of the Martian camera becomes detached from its casing after Gene Barry pounds it to death. When he picks it up and puts it on a table, it rocks forward and comes to rest, facing down, on the table: the tri-lens is now firmly attached to its casing.
Continuity mistake: When the Martian saucer crashes in the farmhouse while Dr. Forrester and Sylvia are eating, a long shot shows the Martian saucer crashing into the side of the house. Then it cuts to an inside shot with the wall (with a window) being smashed from outside in. Then it cuts to an outside shot again showing the meteor having collapsed the side of the house that was caving in, in the inside shot, however the meteor has crushed almost half the house - far more than what was happening in the inside shot.
Continuity mistake: A hatch opens-up to the martian saucer showing a very weak, limp martian arm moving slowly and lying against the door. Next scene shows a wide angle view of the people and the arm but the arm is now touching the belly of the craft. Another scene change has a close-up of the arm again resting on the hatch.