Revealing mistake: When the Operative is reviewing Mal's file, Mal's first name is initially spelled as "Malcom", in the next shot that has been corrected to "Malcolm".
Continuity mistake: When Ice Cube is running out from jail, he kicks out the ventilator and climbs up the roof. Next shot from far, the ventilator is in its place. (00:11:10)
Visible crew/equipment: In the final scene where Evey activates the train full of explosive devices, making it head towards Westminster Palace, a camera mounted on a crane is reflected on the train glass. (02:02:16)