Little is known about the acarofauna associated with wood-boring beetles in Canada, including long-horned beetles (Coleoptera: Cerambycidae). Herein, we assessed the prevalence, abundance, diversity, phenology, and attachment location of mesostigmatic mites (Acari: Mesostigmata) associated with Monochamus scutellatus (Say), and tested whether the abundance and prevalence of mites differed between male and female beetles. A total of 176 beetles were collected in two sites in eastern Ontario in 2008 and 2009 using Lindgren funnel traps baited with α-pinene and ethanol lures, and 71% of hosts had mesostigmatic mites. A total of 2486 mites were collected, representing eight species, four genera, and three families (Digamasellidae, Trematuridae, and Melicharidae). Average prevalence was variable across mite species, and the number of mites per infested beetle also varied across species. Many of the mite species collected in this study have been reported from other cerambycid species, as well as from other wood-boring beetles, such as bark beetles. There was no significant sex bias in the abundance or prevalence of mites between male and female M. scutellatus, which suggests that there is no selective advantage for mites to disperse on females. This study represents the first quantitative investigation of the mites associated with M. scutellatus in Canada.