The northern saw-whet owl is smaller than the eastern screech owl. This is very noticeable if you see one up close in the wild after seeing an eastern screech owl the same day.

Northern saw-whet owls can often be confused with the rarer and slightly larger boreal owl. One way to tell the difference is the markings on the forehead of both owls. The saw-whet has white stripes on the dark brown area of the forehead just between the eyes while the boreal owl has dots instead.