This article presents analyses of lithic and zooarchaeological data from the Kuril Islands and Sakhalin Island in the Russian Far East to better understand the effects of island isolation and biodiversity on human settlement and subsistence. Using the theory of island biogeography, we examine predictions about lithic raw material use, trade, mobility, and foraging behavior for different island groups. This study finds convincing evidence that insularity imposed significant constraints on prehistoric maritime hunter-gatherer access to lithic raw materials and foraging targets in this part of the North Pacific. We find that lithic raw materials are constrained in their distribution and conserved in more insular areas, while zooarchaeological taxonomic composition and richness data pattern according to expectations from optimal foraging theory applied across islands of variable biogeographic diversity. While based on limited samples, the results of these analyses provide support for a biogeographical approach to the prehistory of islands and add to our understanding of human adaptation in the Sea of Okhotsk.