Why do local governments develop policies for the reception and integration of forced migrants? What strategies do they employ in pursuing their own policy objectives in this field, especially within restrictive institutional and financial frameworks? In this article, I use an assemblage approach and insights from extensive desk and field research to study the successful migration policy activism of the Municipality of Thessaloniki in Greece. I argue that the initiatives of mayors and access to external funds can both trigger and facilitate the development of local reception and integration policies. In addition, I argue that horizontal and vertical coalitions with local, transnational and international partners may help local governments effectively exploit their space for discretion in migration and integration policy-making. Based on my findings, I emphasise the need to further examine the emerging relationships between United Nations (UN) organisations and local authorities in the field of migration governance. Furthermore, I advocate a broader application of the assemblage approach in migration policy research.