The Canadian species of the genus Placusa Erichson are reviewed. Eight species are recorded, of which four constitute new Canadian records (P. despecta Erichson, P. incompleta Sjöberg, P. petulans Casey, and P. vaga Casey) and two are new to science (P. pseudosuecica Klimaszewski sp.nov., and P. canadensis Klimaszewski sp.nov.). Placusa turbata Casey, one of the two species previously recorded from British Columbia, is here considered a synonym of P. tachyporoides (Waltl) and is reported for the first time from eastern Canada (New Brunswick, Ontario, Quebec). New data are provided on the systematics, distribution, bionomics, and relationships of selected North American species. A key to the species occurring in Canada is presented with illustrations of the median lobe of the aedeagus, spermatheca, male tergite 8, antennae, and outline drawings of the head and adult forebody for each species. Selected Palearctic species are also illustrated for easy comparison with the closely related Nearctic species. The Canadian distribution is presented on contour maps, and world distribution is discussed for all species. The following lectotypes are designated for the Nearctic species which were described from more than one specimen without former holotype designation: Casey (1893, 1911): P. frosti, P. strata, P. tacomae, P. turbata; Erichson (1840): P. despecta; and Sachse (1852): Oxypoda minuta Sachse. Oxypoda minuta is transferred to the genus Placusa and newly synonymized with P. despecta Erichson (1840).