Radicalization—as a complex process of adopting extremist attitudes—includes maladaptive responses to the transformative power of globalization. Globalization contains sociocultural disruptive and acculturative processes, initiating exclusionary and integrative reactions. These reactions have dissimilarly been associated with aspects of extremism. In seven preregistered studies (N = 2,161), we draw on various methods combining naturalistic circumstances, cross-sectional, longitudinal, experimental, and representative data to scrutinize the complex globalization–radicalization nexus within the contexts of the United States, the United Kingdom, and Pakistan. Our results provide empirical support for the hypothesis that insecure life attachment (i.e., experience of contextual safety, inclusiveness, reliability, fairness, and facilitating well-being) and globalization perceived as a threat can lead to extremism through defensive reactions to globalization. Specifically, we found ethnic protection to be a central mechanism connecting sociocultural disruption and threats with extremism. Globalized radicalization ascends as a contemporary phenomenon reflecting the dark side of global interconnectivity.