This thesis describes multi-scale patterns of ground-dwelling spiders (Araneae), a model arthropod taxon, in northern Canada. First, I examined how ground-dwelling spider diversity (i.e., composition, species richness, evenness and structure) varied at local, regional and continental scale, in three major ecoclimatic regions: the North-Boreal, Subarctic and Arctic. Second, I determined if diversity patterns varied at the family level. Third, I tested whether climate or vegetation explained spatial variation of diversity. Ground-dwelling spiders were collected in 12 sites across northern Canada using a hierarchical nested design. Spider diversity was structured at continental scale across ecoclimatic regions but not by latitude. At regional scale, western sites differed from eastern sites indicating the importance of longitudinal diversity gradients in northern Canada, perhaps due to patterns of post-glacial dispersal. Vegetation and climate explained Arctic diversity patterns of spiders, and thus predicted climate change may alter the distribution of spiders. Our results suggest that historical processes as well as vegetation and climate are important drivers of diversity patterns at continental scale in northern Canada while biotic factors may affect small scale variation in diversity. Due to the large extent and fine resolution, this research contributes to a better understanding of hierarchical patterns of diversity. It also provides baseline data on distribution and diversity of Arctic spiders that will be essential to monitor the effect of environmental changes on biodiversity in northern Canada.