Character mistake: The scene in the outdoor Parisian cafe is incredibly daft. First, the cafe owners call James Coburn's bizarrely-accented New Zealander to the telephone to keep him out of the way as their accomplices assassinate three uniformed German officers seated in the cafe in a drive by shooting. They then toast the killings with cognac, and that is the mistake - not the shootings, not the luring away of Coburn - the mistake is that the cafe proprietors celebrate the assassination of the German officers in broad daylight, in the open, without even stopping to think that such an action would have them shot, because all of this is done in the direct view of passers-by in broad daylight. Do they think those three German officers were the only ones in Paris? How did they know Coburn wasn't an undercover Gestapo agent or a French collaborator? Don't they stop to consider that in an occupied city machine gun fire is going to draw some attention from the authorities, who might just wonder what a couple of bullet riddled corpses are doing lying about the place?
Other mistake: When Hilts and Ives are taken down to the cooler for the very first time, just after arriving at the camp, watch the wall as the door is closed by the guard behind Ives - it very obviously moves as the door slams shut.
Character mistake: When Sedgwick is bringing the cement tunnel lid to Willy, somebody yells out "Hey Hendley" and Sedgwick answers "Hello boys". He was called by the wrong name.
Visible crew/equipment: Late in the film, when the two escapees are boarding a bus, there's a studio lamp on a scissor-lift in plain sight at the left side of the screen.
Other mistake: Ramsay sports on his tunic the ribbons for the Distinguished Service Order, the Military Cross, either the 1914 or 1914/15 Star, the British War Medal and the Victory Medal. Unfortunately, the ribbon bar for the last three has been sewn onto his tunic upside-down - it reads, left to right as seen, VM, BWM, Star, when it should read Star, BWM, VM.
Continuity mistake: In the end of the movie, Hilts (Steve McQueen) is returned to the camp - he is dirty and his shirt is torn. When he enters the cooler, after being tossed his baseball glove, he is clean and his shirt is no longer torn.
Continuity mistake: When Roger is in the van talking to Macdonald, his face is deliberately dirty and stubbled - but when they are about to shoot him, he is clean-shaven. similarly with his bruises which seem to magically disappear by the evening of the first day.
Factual error: When McQueen steals the motorbike from the German soldiers and rides off it is clearly a Triumph, a British make, not a BMW or Zundapp which was what the German army used. More to the point it looks like a 1960s model.
Plot hole: Blythe doesn't need to escape - thus endangering fellow escapees and taking the place of another man - since the Geneva Convention (which the Luftwaffe generally adhered to as the Allies held many German prisoners) required that all POWs who suffer severe disability that would prevent them from fighting were to be repatriated.
Continuity mistake: When Hendley and Blythe get into the German aircraft first, the cockpit is tiny and cramped, like you'd expect. However, when they cut to the studio-done flying scenes, it suddenly becomes much larger, nice and roomy.
Continuity mistake: In the scene in which the POWs are distributing the tunnel dirt over the compound, Hendley is leading a group of POWs in a soldier's march. In one shot, dirt is coming out from the bags inside their trousers, but their hands are visibly swinging back and forth; they can't be pulling the strings in their pockets to release the dirt.
Continuity mistake: While describing the escape process, Roger says that "Tom will run north from the 105." He is interrupted, then says, "as I said, Tom will run north from 104."
Plot hole: Roger's initial briefing at the beginning of the film states that 'Tom' goes out from 104 and 'Harry' from 105. Despite this the goons are said to be in 105 when they find the entrance to Tom.