The impact of a program or policy intervention is influenced by the impact synergies from other programs and policies, and by the role of underlying institutions. This fact, though known, has not been formally treated in existing literature. This paper addresses this gap by developing a framework that evaluates together the impact synergies among multiple programs and the impact mediation roles of different institutions within the same analytical context. An application of this framework in the Sri Lankan context provides numerical evidence for the flow of impact synergies among three water and agriculture-related development programs and the roles of eleven different institutions.