Factual error: When Rick is talking about the German guns shelling near Paris, he describes them as 77's (non-existent) - likely meant the famous 88's used as anti-aircraft and tanks as well as for wheeled guns. [The line was originally "88s" but was changed at the request of the War Dept. so as to not tip the German's hands that we knew about the 88s.] (00:44:25)
Factual error: Major Strasser uniform trousers have a double stripe running down the side. Double stripes were reserved for General Officers therefor Strasser would not be entitled to wear them.
Factual error: Major Strasser refers to Rick as a "bumbling American." Capt. Renault then replies, "We mustn't underestimate American blundering. I was with them when they blundered into Berlin in 1918." During World War I, no Allied soldiers ever attacked or occupied Berlin. In fact, when the war ended Germans still occupied some French territory. This led in part to the rise of Hitler and World War II because of the belief that Germany did not really lose World War I but was sold out by various conspirators.
Factual error: The extras in the film that were supposed to be Moroccans are perfectly dressed as Egyptians.
Factual error: The opening credits name S.Z. Sakall as S.K Sakall, and the globe of the world which follows the credits has the USSR listed as the Union of Socialist Soviet Republics. The original name of the USSR in Russian was "Soyuz Sovetskikh Sotsialisticheskikh Respublik" which translates as Union of Soviet Socialist Republics.