It was not until the 1980''s that concerns about the migration and security nexus first appeared in post-World War II Europe. Since then, a growing Muslim presence in Europe has notably affected the European security agenda. The first part of this monograph will critically review relevant international relations studies concerning security and Muslim migration to Europe. The second part will analyze Muslim migrant impact on European security perceptions and policy, with a focus on Germany, France and the United Kingdom. Socio-economic fears, concerns over reactive conflict spillover to migrant communities, and impact of Muslim political participation in host states have led to securitization of new issues and re-conceptualization of traditional European security concerns. The monograph maintains a fine balance between theory and empirical evidence, and as such it will be of interest to students, practitioners and scholars of international relations, comparative politics, migration studies, and European politics.