Continuity mistake: When Kate and Carly are leaving Carly's apartment building and Carly goes to hail a cab, Kate is wearing a cream cardigan over her blue and white outfit, standing by the curb holding the dog's leash. The scene cuts closer and Kate is not wearing the sweater at all. (00:31:55)
Continuity mistake: When Nick approaches the desk to ask for Carly, you can see the conference room has frosted glass. When Nick walks through the glass of that conference room, it's clear glass. (01:35:57 - 01:41:01)
Continuity mistake: When Cameron Diaz is talking to Leslie Mann about going to the Bahamas, from shot to shot, Cameron Diaz's hair is behind her ear, then not, then behind her ear again, then not.
Continuity mistake: Toward the end of the film when Frank confronts Mark outside of Carly's office building, he winds up to deliver a roundhouse punch yet the punch is a jab.
Continuity mistake: In the scene when Kate is in her wedding dress crying and Carly comes over to her house to check on her, the girls are upstairs and Mark comes home early. Kate shoves Carly out the bedroom window on the second floor, who falls through a lower roof and onto the ground. In the next shot, Carly is lying on the ground surrounded by a bunch of white 2x4 boards that have suddenly appeared.