This dissertation examines how and to what extent the interplay of actors and institutions shape public agricultural budget outcomes in Nigeria, within the framework of actor-centered institutionalism. Through a single-case study of agricultural public expenditure decision-making in Nigeria with within-case analysis, this dissertation examines: i) how the structure of intergovernmental relations affects the roles and incentives of government tiers in the joint provision of public agricultural goods and services; ii) how formal budget rules and informal budget practices affect the roles and incentives of key actors in the federal agricultural budget process, the nature of the interactions between actors in the budget process, and the features of the budget process itself; iii) how and to what extent actors' perceptions, preferences, capabilities, constellations, and mode of interactions within the institutional architecture that governs public expenditure decision-making processes shape subnational agricultural budget outcomes in Nigeria. The dissertation employs in-depth, semi-structured interviews with over 100 key informants at the federal and subnational levels, including government officials, donors, policy analysts, and policy advocates to explain public agricultural budget outcomes in Nigeria, focusing on the interplay of actors and institutions. By doing so, it tried to shed light on the puzzle of underinvestment and misinvestment in African agriculture. This dissertation contributes theoretically, empirically, and methodologically to literature on the political economy of public expenditure decision-making in Africa. Implications for research and policy as well as potential avenues for future research are provided.