Continuity mistake: When Toula goes to meet Ian at the school where he works, and they are talking in the hallway, her arms occasionally move from behind his neck to the front of his shoulders. The continuity is correct at the bgeinning of the scene, but at the end it happens a few times.
Revealing mistake: Near the end when Toula and Ian are in the limo, Toula starts to wipe off her makeup and take off or loosen her wedding dress. She actually pulls off the bow on the right arm of her dress. If you pause the movie right there, you can see by Ian and Toula's reaction the bow was not supposed to be removed. The scene ends immediately after.
Factual error: In the scene where Toula removes the 'Computers and Tourism' flyer from the bulletin board, there is another flyer in the top left of the screen advertising the 2001 Class of Ryerson. Ryerson University is located in Toronto, while the movie is supposed to be set in Chicago.
Continuity mistake: When Ian asks Toula to marry him, before he does it, they are lying in bed talking. During the first shot, she is playing with his face with her left hand, and when the view changes to her, in the bottom left corner of the screen, you can see part of the same hand on her stomach. In the next shot of him, her hand is on his face again. This continues to switch throughout the scene.
Continuity mistake: When the next door neighbour brings back Toula's grandmother to her father, the camera angle from the front shows his right hand on her right arm near her shoulder. When the camera angle changes to a rear view, his hand is now on her shoulder. Happens twice during the scene.