Continuity mistake: In the scene with the lovely dancing ladies, Cotten blows cigar smoke just before a cut to him from the opposite angle. From this angle there is no smoke. This takes place just before Wells throws his jacket to Cotten.
Continuity mistake: Kasper Gutman goes wild cutting the Maltese Falcon continuously with his knife, but in one of the inserted close-ups of him he's just standing there not doing anything. (01:28:40)
Continuity mistake: Ferdie squirts oil on the face of Chuck. Chuck wipes his hand across his face and slaps Ferdie, leaving oil on his cheek. In a close-up, Ferdie cleans his face with a handkerchief but when he pulls the handkerchief away, there is no oil on it. The oil had obviously been cleaned off his cheek before the scene was filmed.
Continuity mistake: Johnnie, Lina and Beaky are playing anagrams. Lina spells out the word MURDER with an M as the first letter. The shot cuts away and then back again, and now the first letter is an inverted W. (01:01:40)