We identified species of mites phoretically associated with mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), collected from bolts of lodgepole pine, Pinus contorta Douglas ex Louden (Pinaceae), and pheromone-baited traps in northwestern Alberta, Canada. Mite load and species composition were compared between beetle sexes and with beetle emergence time and estimated body size. The vast majority of mites associated with D. ponderosae in Alberta belonged to three species: Proctolaelaps subcorticalis Lindquist (Acari: Mesostigmata: Melicharidae), Histiogaster arborsignis Woodring (Acari: Astigmatina: Acaridae), and Tarsonemus ips Lindquist (Acari: Prostigmata: Tarsonemidae). There was no difference in mite loads on male and female beetles recovered from bolts in the laboratory and those from pheromone-baited traps in the field. More mites were found on larger beetles in the laboratory, but only T. ips showed this pattern on field-trapped beetles. There was no relationship between total mite load or load by mite species and beetle emergence time in the laboratory, but total mite load on field-trapped beetles decreased over the collecting season (10 June – 3 September 2009) at five collection locations (Grovedale, Blueberry Mountain, Hythe, Evergreen Park, and Glenleslie). This study is the first to document the assemblage of phoretic mites on D. ponderosae in Alberta and will help to direct future research on their interactions.