Public administration, public policy, and political economy literatures are increasingly preoccupied with the role of agency in policy and institutional change, and the effects of institutions on the agency of individual actors. However, linkages between policy and institutional entrepreneurship in processes of institutionalization remain a black box. This article aims to fill this void. It contributes to our understanding of processes underlying the institutionalization of policy ideas in the public sector that have not been investigated adequately. Based on an exploratory case study of the introduction and institutionalization of macroprudential policies to contain macro-financial risks in Turkey, this article argues that policy and institutional entrepreneurship processes are inextricably intertwined and fundamental to the institutionalization of policy ideas: the institutionalization of new policy ideas that resolve conflicting institutional logics and facilitate cooperation and/or collaboration in inter-bureaucratic policy formulation and implementation is most likely when an individual agent with the requisite resources and capabilities builds coalitions through combining the policy and institutional entrepreneur roles while undertaking discursive and powering strategies.