Factual error: In one scene, focused on a period wood-staked pickup truck parked on the street, you can see clearly a modern Jeep Grand Cherokee parked on the other side of the street.
Visible crew/equipment: When the guy on the roof stands and takes aim at the window in preparation for Brian, the film crew are reflected in a window behind him. (00:13:00)
Continuity mistake: When Alan and Doug the drug dealer are suggesting more accurate names for roofies, Doug places one hand on his hip with the other down by his side, but in the next shot, both hands are resting on his stomach. (01:21:30)
Continuity mistake: At the very beginning, when Quaid has finished showering and is picking his phone, wallet, badge, keys, etc, there is a shot of his hand as it is picking up his cellphone. Cut to a wide shot of him and the objects have moved. For example, the coins have become a close cluster, his pack of cigarettes is no longer on the newspaper, and his badge has switched places with the lighter. (00:02:45)
Character mistake: While examining "Diagramma della Verita" in the Vatican archives, Langdon is careful to use a cotton glove and a pair of tongs to turn the pages. But when he returns later to search the Bernini texts for clues about the "fire" church, he turns the book pages with his bare hands. (00:36:30 - 01:04:55)
Continuity mistake: At the start when Simone is telling Eddie to wake up he has his hand on his chest. Camera changes and it's not. (00:01:50)
Character mistake: The opening shot of the movie pans across a fence supposed to enclose the hunting reservoir of the royal family of the fictitious kingdom of Vespania. Judging by the sign on the fence, the official language of the country must be EngRish; the sign says "Land Demesne We knownothing [sic] about FIRE!", citing also as source for these cryptic messages the "internal secuLity act of 1950." (00:00:01)