Despite being an uncommon topic in sociological inquiry, collective defense mechanisms are a widely known phenomenon in social life. Whenever people experience anxieties in common, shared defensive processes can arise at an unconscious level, shunting off these anxieties from reflective awareness. This can happen in social and organizational settings that are intimate and impersonal, small and large, short-lived and enduring. How can we better theorize collective defenses and their role in the social world? This article demonstrates how coordination mechanisms can align individual defenses into shared defenses, a micro-to-macro transition. It explores how collective defenses can take on a variety of empirical forms, whether as interaction-order dynamics, cultural discourses and narratives, or institutionalized rules and arrangements. And it shows how this understanding of collective defenses can be incorporated into still larger frameworks of inquiry into power and inequality in social life. It also suggests ways in which methodological innovations can help the study of these shared defenses become more transparent, nonarbitrary, and rigorous, allaying concerns sociologists long have had about investigating unconscious processes. By highlighting the formation, deployment, and potential undoing of collective defense mechanisms, this article illuminates an exciting new terrain for sociologists to explore and opens up new possibilities for more constructive and non-defensive real-world problem solving.