<p>To control irregular migration, many destination countries try to find ways to outsource their liabilities to third countries or deter migration at its origin. This article offers an examination of the cascading effects of externalization practices for migration deterrence, documenting how transit countries in the Global South reproduce the externalization processes of destination countries in the Global North by domestic and/or external space-making practices. By integrating analyses of primary data with secondary resources, this article contributes to studies of externalization and argues that spaces of <i>double-layer deterrence</i> are created by transit countries to control the mobility of irregular migrants toward destination countries. The article conceptualizes double-layer deterrence through the case study of Türkiye, focusing on the transit space and space-making strategies. The study then compares these practices in Türkiye and Mexico by offering a multidimensional approach to assess key patterns of double-layer deterrence in transit countries. The article concludes that double-layer deterrence, as a set of spatial barriers executed by transit countries, is a rising phenomenon and brings a new understanding to deterrence practices against irregular migrants, obstructing their path to permanent protection.</p>