Character mistake: When Jeebs is showing them his deneuralizer and it shorts out a moment, he states he's still running off the 6.0. However the computer display shows he's using the beta 0.93.
Visible crew/equipment: When Jay is addressing the civilians in the small section of the subway car that is left after Jeff ate the rest, green screens are reflected in Will Smith's sunglasses before he neuralizes them.
Continuity mistake: At the post office, K waves his hands at J and turns around to where the employees are. When the angle changes K is waving his hands again.
Continuity mistake: Serleena's ship lands completely perpendicular to the ground, but when the angle changes it's pointing a 2 o'clock position.
Continuity mistake: When they land on the roof of the launch site, Jay gets out of the passenger side, even though he and Kay switched spots after which Jay was driving/flying.