The Northern Barrens tiger beetle (Cicindela patruela patruela, Dejean 1825) (Coleoptera: Carabidae) is globally rare and endangered in Canada. We know very little about this species' behavioral ecology and despite there being only 2 remaining populations in Canada, we know very little about either's demography. Here, we use capture–mark–recapture methods to estimate population size and movement of individuals on Île-aux-Allumettes (Quebec, Canada). We found that the population on Île-aux-Allumettes is small—approximately 102 individuals—but this appears to be typical for this species and tiger beetles in general. Beetles on Île-aux-Allumettes traveled approximately 33 m per day with no observed difference between the sexes in mobility. We did not find any morphological correlates of mobility, but we did find that females are significantly wider, but not longer, than males. Because the number of C. p. patruela on Île-aux-Allumettes is small and the population is isolated, we recommend that managers continue to monitor the population and consider translocations to augment population numbers and to reduce the negative consequences of demographic and genetic stochasticity, such as inbreeding.