In this paper, we report on the diversity and distribution of Dytiscidae (Coleoptera: Adephaga) collected in Far North Ontario, Canada during the years 2009 to 2014. A total of 387 individuals from 34 species and 14 genera were collected, which represent 20.9% of the known Ontario fauna. Of these, 24 species are Nearctic (70.6%) and 10 species Holarctic (29.4%). Most species have a transcontinental distribution in Canada and are characteristic of the Boreal Ecozone. Two species, Hygrotus unguicularis (Crotch, 1874) and Nebrioporus depressus (Fabricius, 1775), are recorded in Ontario for the first time. The collection of black-bodied Nebrioporus macronychus (Short and Angus, 1992) in this study is a unique feature amongst North American species of Nebrioporus Régimbart, 1906.