Continuity: The dates on Templar's bank account transactions do not match the dates he gives in his narration. When he transfers the microchip money, the dates on his computer are for March. A few days later, when he is scouting Emma's apartment, he records the date as November.
Continuity: When Tretiak arrives in front of the US embassy in search of Templar and Russel, his Land Rover 4.0 se has original equipment proper wheels on it. However, after it explodes and lands, we can see that it now has the three spoke wheels from the earlier generation Range Rover County.
Revealing mistakes: Agnes is on the wrong side of the banister when the dogs jump at her. When she falls she is on the same side as Simon, yet when she goes to kiss him she is on the other side. Had she been on that side she wouldn't have been knocked down.
Continuity: In the middle of the airport lounge, Simon orders a cup of coffee, which is then delivered to him 2 seconds later by the same waitress.
Factual errors: When Dr. Emma Russell gives her lecture at Oxford about her amazing cold fusion breakthrough, the lecture takes place in the 1st and 2nd year undergraduate teaching laboratory most likely because it looks "sciencey." No lectures are given in this room, even the most mundane, never mind something of this importance.
Continuity: Arm position of the red-headed student who asked a question during Emma's lecture.
Continuity: When Emma enters Simon's English country house she leaves the door wide open and continues into the room. In a subsequent shot, the door is closed.
Continuity: When Emma and Simon meet in England (after Moscow), there is a flipped shot where Simon's mole and Emma's scar swap sides on their faces.
Revealing mistakes: When Emma first climbs into the underground pipe system with Simon, you can see that she is wearing black athletic knee pads, thanks to the visible white label that says "Trace", an athletic gear brand.
Factual errors: When Emma is looking through suspect sketches at New Scotland Yard with the two detectives, the female detective says that the suspect is known by many different names, including "Louie" (or "Louis") "Guanella". Emma's response is "Of course... all names of Catholic saints." In the case of "Louie Guanella", this is incorrect. Luigi Guanella was a Catholic priest from Northern Italy, born in 1842 and died in 1912. Guanella was beatified in 1964 but has NOT yet been canonized (made a saint) by the Roman Catholic Church. He is therefore referred to as Blessed Luigi Guanella, not Saint (Luigi) Guanella.
Continuity: While fleeing "Tretiak's goons" on the rooftop of the apartment building, Simon is wearing a black hat. When he follows Emma through the roof access, the hat has disappeared and his hair is perfectly styled.
Revealing mistakes: When Ilya Tretiak (Ivan Tretiak's son) holds up the Simon, while he is stealing the microchip in the beginning of the movie, you can see in the front of the gun that the revolver isn't loaded.
Errors made by characters (possibly deliberate errors by the filmmakers): When Templar is attempting to cut trough the barrier of solid iron in his escape in the sewer by using a blowtorch, he doesn't put the tip of the blue torch at the surface, he put the middle of the yellow torch at the surface. This method would require hours of work.
Continuity: The young Simon Templar is obviously left-handed, but the older Simon Templar is right-handed.
Plot holes: When Dr. Russell is shown the sketches of Simon's saint alter-egos, the nerdy reporter is in the pack. At the end she is surprised to find out he was the nerd, and the detective from Scotland Yard sitting next to Simon does not recognize him in his nerd persona.