Abstract: In federal states, constituent units play an important role in affordable housing policy. Nevertheless, insights into affordable housing policy in federations are lacking. To lay the grounds for future research about an increasingly salient policy field, this research note explores the degree of de/centralization in affordable housing policy in Australia, Austria, Canada, and Germany, focusing on the two main policy instruments: social housing and the housing allowance. The research note develops an analytical framework that allows the examination of the relative significance of the federal government and the constituent units, and it applies this framework to the four countries. The research note highlights that legislative authority often does not fully capture the degree of de/centralization. Governments’ decision to provide a policy instrument, the relative importance of policy instruments, the provision of conditional grants, and the existence of a functional division of powers must also be considered.