Scholars in many fields have long recognized the role that social and professional networks play in the diffusion of innovations. However, among political scientists, an awkward separation has emerged between scholars investigating policy diffusion processes and those investigating policy networks and, more generally, the role of ideas in politics. In this article, we present a theoritical argument for integrating insights from policy networks studies into diffusion studies. Since they face clear incentives to tap the resources of policy networks, we give policy entrepreneurs a prominent place in this discussion. Using event history analysis models of the diffusion of school choice ideas across the United States, we test the empirical relevance of our discussion and find that greater involvement in policy networks significantly increases the likelihood of policy entrepreneurs achieving their legislative goals. Based on our theoretical discussion and these empirical results, we suggest that political scientists investigating the diffusion of policy innovations should pay careful attention to the role that policy networks play in this process.