A review of the Nearctic genera and Canadian and Alaskan species of the Ocalea group is presented. Ten genera are treated, with five erected as new: Alfocalea Klimaszewski gen. nov. (type species: A. montana Klimaszewski sp. nov.), Betocalea Klimaszewski gen. nov. (type species: B. pacifica Klimaszewski sp. nov.), Gennadota Casey (reinstated), Longipeltina Bernhauer, Megocalea Klimaszewski gen. nov. (type species: M. lemieuxi Klimaszewski sp. nov.), Metocalea Klimaszewski gen. nov. (type species: M. lindgreni Klimaszewski sp. nov.), Neoisoglossa (Casey) (nomen novum), Neothetalia Klimaszewski gen. nov. (type species: N. nimia (Casey)), Ocalea Erichson (restricted definition), and Parocalea Bernhauer. Twenty-four species of the Ocalea group are here recognized in the Nearctic region, fourteen of which occur in Canada. Six new species are described from western Canada and Alaska: Neothetalia smetanai Klimaszewski sp. nov. (Canada: British Columbia), Neothetalia canadiana Klimaszewski sp. nov. (Canada: British Columbia, Yukon Territory; United States: Alaska), Betocalea pacifica (Canada: British Columbia), Alfocalea montana (Canada: Alberta, British Columbia), Metocalea lindgreni (Canada: British Columbia), and Megocalea lemieuxi (Canada: British Columbia). The first record of Neoisoglossa agnita (Casey) in Alberta is provided. Two nominal species, Atheta (Athetalia) bicarniceps Casey (= Neoisoglossa) and Isoglossa grandicollis (Casey) (= Neoisoglossa), are here synonymized with Neoisoglossa arcuata (Casey). Aleochara pallitarsis Kirby has been transferred to the genus Neothetalia and is newly recorded from Alaska and British Columbia. Ocalea columbiana Klimaszewski has been transferred to Neothetalia and is newly recorded from Alaska. Neothetalia pallitarsis was formerly recorded from an unknown locality in North America and Neothetalia columbiana from the Carmanah Valley on Vancouver Island. Neothetalia nimia is newly recorded from Alaska. A new generic classification is proposed to accommodate species of the Nearctic Ocalea group. New data are provided on the systematics, relationships, bionomics, and distribution of the Nearctic species and genera of America north of Mexico. Diagnoses, colour images of entire bodies, and line illustrations of genital features are provided for those Canadian and Alaskan species that were not formerly illustrated, and their collection localities are plotted on maps. A key to Nearctic genera of the Ocalea group and the species occurring in Canada and Alaska is presented. The lectotypes have been designated for the following nominal species because the original series consisted of syntypes or represented mixed species or both sexes but with males bearing a better diagnostic set of characters: Aleochara picata Stephens (= Ocalea), Atheta (Athetalia) bicarniceps, Atheta (Athetalia) nimia Casey (= Neothetalia), Atheta (Athetalia) repensa Casey (= Neoisoglossa), Isoglossa arcuata Casey (= Neoisoglossa), Ocalea agnita Casey (= Neoisoglossa), Ocalea franciscana Casey (= Neoisoglossa), Ocalea fusca Fenyes (= Neoisoglossa), Ocalea grandicollis Casey (= Neoisoglossa), Pyroglossa grossa Bernhauer, Rheobioma disjuncta Casey (= Neoisoglossa), Rheobioma marcida Casey (= Neoisoglossa), and Rheobioma terrena Casey (= Neoisoglossa).