— Institutions matter within natural resource management. While there are many examples of analyses of the nature and influence of institutions within fisheries, there are fewer examples of how institutions inform the practice and outcomes of comanagement. This article reports on analysis of institutions and fisheries co-management in East African and Malawi inland fisheries informed by Critical Institutionalism. It concludes that relations between fisheries departments and local co-management structures, and between local government/traditional authorities and local co-management structures, and social, power, and gender relations within and beyond fisheries communities, particularly impact on the practice and outcomes of co-management.