The western Canadian and Alaskan species of CorticariaMarsham, 1802 are reviewed. After this review, there are 29 species recognized from western Canada and Alaska. The following are reported for the first time from North America: Corticaria kabakovi Saluk, new continent record; and for the first time from Canada: Corticaria arctophila Fall, Corticaria cavicauda Fall, Corticaria fulva (Comolli), Corticaria inconspicua Wollaston, Corticaria planula Fall, and Corticaria prionodera LeConte, new country records. Twelve new species are described from Canada: Corticaria alta Hammond and Chambers, Corticaria arborea Hammond and Chambers, Corticaria bousqueti Hammond and Chambers, Corticaria cylindracea Hammond and Chambers, Corticaria langori Hammond and Chambers, Corticaria maritima Hammond and Chambers, Corticaria montana Hammond and Chambers, Corticaria pseudofennica Hammond and Chambers, Corticaria pseudoincerta Hammond and Chambers, Corticaria pseudopinetorum Hammond and Chambers, Corticaria pseudovicollis Hammond and Chambers, and Corticaria pseudotsuga Hammond and Chambers. An additional two new species are described from Montana: Corticaria andrewsi Hammond and Chambers and Corticaria aspera Hammond and Chambers. After examination of North American type material the following nomenclatural and taxonomic changes are proposed: Corticaria dentigera LeConte is placed in synonymy with Corticaria rubripes Mannerheim, new synonymy; Corticaria grossa LeConte is taken out of synonymy with Corticaria pubescens (Gyllenhal) and instead is placed in synonymy with Corticaria punctulata Marsham, new synonymy; Corticaria valida Fall is placed in synonymy with Corticaria aphictoides Reitter, new synonymy; Corticaria varicolor Fall is placed in synonymy with Corticaria impressa (Olivier), new synonymy; Corticaria falliHetschko, 1929, should be adopted in lieu of Corticaria cribricollisFall, 1899, as the latter is a junior primary homonym of Corticaria cribricollisFairmaire, 1863; and the following names are declared nomina dubia until type specimens can be located: Corticaria canaliculataMannerheim, 1853; Corticaria columbiaFall, 1899; Corticaria salpingoidesMotschulsky, 1867; and Corticaria spinulosaMannerheim, 1852. A key to the Canadian and Alaskan fauna and discussion of all current North American species is provided.