The Eurasian beaver (Castor fiber) was an important member of Early and Mid-Holocene landscapes and ecosystem communities in Northern Europe. Previous zooarchaeological research has established the alimentary roles of beavers for Mesolithic forager societies and the importance of these animals for fur procurement. We develop an integrated biocultural approach to human-beaver interactions and examine the position of humans and beavers in Mesolithic and Early Neolithic multispecies systems. We contextualize beaver landscape agency in hydroactive environments at the edge of former glaciers with human foraging and landscaping behaviour, especially fish-getting practices, and beaver-related material culture documented in the archaeological record of Northern Europe. This cross-cultural, diachronic analysis reveals previously overlooked facilitations of human behaviour by beaver practices and ecological legacies. We argue that Mesolithic beaver-related material culture is therefore also a result of the cultural keystone status of Castor fiber in higher latitude Early and Mid-Holocene landscapes, indicating that post-glacial human settlement in many parts of Northern Europe reflects adaptations to beaver-engineered riverine wetlands and multispecies affordances. We further suggest that long-term trajectories of human-beaver cohabitation differed between northern European regions. While in Southern Scandinavia, human-beaver intersections witnessed major re-organizations during the Mid-Holocene, beavers retained a key role for human societies across the Baltic and Northwestern Russia throughout much of the Holocene and played an important role during the Mesolithic-Neolithic transition in the Dutch wetlands, suggesting that evolved human-beaver systems were unequally affected by developing human lifeways in this pivotal period of human prehistory.