We describe a rare case of acute mania in the setting of autoimmune adrenalitis. A 41-year-old male with no previous psychiatric diagnoses presented with impulsivity, grandiosity, delusions of telepathy, and hyperreligiosity following a previous hospitalization for an acute adrenal crisis and 2 subsequent days of low-dose corticosteroid treatment. Workups for encephalopathy and lupus cerebritis were negative, raising concern that this presentation might represent steroid-induced psychosis. However, discontinuation of corticosteroids for 5 days did not resolve the patient's manic episode, suggesting that his clinical presentation was more likely new onset of a primary mood disorder or a psychiatric manifestation of adrenal insufficiency itself. The decision was made to restart corticosteroid treatment for the patient's primary adrenal insufficiency (formerly known as Addison disease), coupled with administration of both risperidone and valproate for mania and psychosis. Over the following 2 weeks, the patient's manic symptoms resolved, and he was discharged home. His final diagnosis was acute mania secondary to autoimmune adrenalitis. Although acute mania in adrenal insufficiency is quite rare, clinicians should be aware of the range of psychiatric manifestations associated with Addison disease so that they can pursue the optimal course of both medical and psychiatric treatment for these patients.