The role of philanthropic foundations in the policy process is largely hidden and thus significantly under conceptualized. In this paper, we argue that several key characteristics of foundations serve as advantages for them to play an intermediary role in different stages of the policy process. By leveraging their independent resources, credibility, and strategic giving, they are able to build coalitions of interest to advance and secure preferred policy alternatives through agenda setting, policy diffusion, and coordinating implementation efforts. We provide evidence for this intermediary role through two qualitative case studies, (1) the Pew Charitable Trust's efforts to promote universal pre-kindergarten, 2002-2012, and (2) multiple foundations' role in supporting extended foster care in California, 2008-2012. In both cases, we find that foundations wielded significant political power within policy communities by serving as central hubs of information, facilitating coordinated action, incentivizing action, and connecting diverse actors. This allows them to play a crucial, yet veiled, role in attempts to advance policy change. This phenomenon may be welcomed for supporting evidence-based policymaking and capacity building, but is troubling in regards to transparency and accountability.