Crime prevention is typically presented in a tripartite model that includes primary, secondary, and tertiary domains. Almost every criminal justice intervention constitutes tertiary prevention and occurs reactively, in the aftermath of an offence. Child sexual abuse is no exception, and prevention science has long recommended we focus our intervention efforts further upstream. Such an approach would include earlier detection and disclosure (secondary prevention), or—even better—reducing the risks of early exposure to the environmental forces which facilitate sexual abuse in the first place (primary prevention). What is missing from the field, however, is a coherent framework through which to critique the unintended consequences of our well-intentioned responses to child sexual abuse. Such consequences include secondary trauma for victim survivors and vicarious trauma for families and practitioners. In this article, we reflect on prevention from a critical perspective that centres the principle of “first, do no harm.” In doing so, we introduce the notion of ‘quaternary prevention’ for child sexual abuse. Public health has long recognised the risks of medicalisation, overdiagnosis, and unnecessary intervention. We encourage our field to engage within a framework of quaternary prevention to consider the iatrogenic effects of many contemporary practices and to take seriously the “do no harm” principle to improve practice across all levels of prevention.