Continuity mistake: After Evangeline has left with Aunt Adelaide, Nanny McPhee enters the children's room, and as she and Chrissie walk to the bed they pass Eric's, Lily's and Tora's beds, with the bare wood floor at the center - there is no rug. However, when Nanny McPhee leaves their room the long red and white rug is at the center of the floor, between all the beds.
Continuity mistake: When Eric, Tora and Aggy are getting ready for bed, Simon walks in and mocks, "And since when have we decided to do what we're told?" The towel to his right (viewer's left) is rumpled up, yet hangs straight in previous and following shots, then is rumpled again.
Continuity mistake: When Mrs. Blatherwick sits in the rocking chair in the kitchen, before the "mouse" races across the floor, in the first shot her left hand lies on her belly, with her right hand over her left, patting it gleefully. When it cuts to a close-up, her hands are in the opposite position.
Continuity mistake: At the end of the movie when the father is getting married to Mrs. Quickly, there is a food fight where the cakes and such are being thrown at everyone. When the father gets green frosting on his face first he has a spot of frosting on the left side of his face, then it is gone, then it's back on his face, then it becomes two spots.