In this article, we analyze the diffusion of liberal and illiberal asylum policies across liberal and illiberal states worldwide. We focus on liberal National Asylum Frameworks (NAFs), which formalize asylum procedures, and illiberal Safe Third Country Policies (STCPs), which restrict asylum by designating other states as responsible for protection. Using a dataset covering 193 UN states from 1951–2021, we first map global trends in NAF and STCP adoption. Our findings show that Europe has led in policy adoption, with NAFs and STCPs often adopted simultaneously rather than consecutively, thus complicating the assumption of a clear illiberal turn. While both policies have also spread globally, however, many states still lack NAFs. We then apply a typology of diffusion mechanisms – rights-driven and interest-driven (rationalist) and ideology-driven and recognition-driven (constructivist) – to explain the diffusion of these policies. We find that rights-driven diffusion is relevant for both policies in Europe, while interest-driven diffusion, especially when triggered by negative policy externalities, has influenced their diffusion globally. Ideology-driven diffusion has spurred NAF adoption, whereas recognition-driven diffusion has a weak influence on STCP adoption. By systematically disentangling and measuring these mechanisms, this study significantly advances diffusion research and provides new insights into global asylum policy diffusion.