Malingering is a medical diagnosis, but not a psychiatric disorder. The label imputes that an evaluee has intentionally engaged in false behavior or statements. By diagnosing malingering, psychiatrists pass judgment on truthfulness. Evaluees taking exception to the label may claim that the professional has committed defamation of character (libel or slander) when the diagnosis is wrong and costs the claimant money or benefits. Clinicians may counter by claiming immunity or that the diagnosis was made in good faith. This problem has come into focus in military and veterans' contexts, where diagnoses become thresholds for benefits. Through historical and literary examples, case law, and military/veterans' claims of disability and entitlement, the authors examine the potency of the malingering label and the potential liability for professionals and institutions of making this diagnosis.