Victims of injustice are prominent protagonists in efforts to resist injustice. I argue that they have a duty to do so. Extant accounts of victims’ duties primarily cast these duties as self‐regarding duties (say, of Kantian self‐respect) or duties based on collective identities and commitments. I provide an account of victims’ duties to resist injustice that is grounded in the duty to assist. I argue that victims are epistemically privileged with respect to injustice and are therefore uniquely positioned to assist fellow victims. Primarily, they discharge this duty through testimony: victims alert other actors to the need for assistance and initiate and coordinate resistance efforts. I briefly provide an account of oppression that ranges from persecution to structural injustice. Through the examples of torture and ‘manterrupting’, I illustrate the duty and its limits. I outline shortcomings in victims’ epistemic privilege and explore means by which these can be overcome. I respond to objections from demandingness and fairness, arguing that victims have an essential, albeit circumscribed, role to play in defeating injustice.