They can weigh from 54 to 151 g (1.9 to 5.3 oz) with an average of around 80 g (2.8 oz), making them one of the smallest owls in North America. In relative size to other owls they are close to the size of an American Robin.
The Northern Saw-Whet Owl makes a repeated tooting whistle sound.
Their habitat is coniferous forests, sometimes mixed or deciduous woods, across North America.
They mainly eat small organisms with a focus on small mammals in their diet. In a test done by Swengel and Swengel they found that the Northern Saw-Whet Owls most often eat deer mice, 67% and voles, 16% of the time in Wisconsin. In a similar test done by Holt and Leroux in Montana found that these owls ate more voles than other mammal species.