How do policy makers learn from each other? Incorporating theoretical insights from research on policy learning, this study provides a novel framework for exploring learning in policy diffusion processes. It differentiates between four forms of learning: instrumental, ideological, normative, and epistemic learning. Each form is based on specific assumptions about the underlying behavioral micro-foundations of policy makers and the actors that play a core role in the transfer of knowledge. The prevalence of these forms of learning is tested in the Swiss context by focusing on two policies in the field of migration where considerable variation is observable between cantons. Using a novel survey experiment among members of cantonal parliaments allows me to assess these learning processes among individual policy makers. Findings of this research will be relevant for scholars interested in both policy diffusion and migration policy making.