A 22-yr-old, captive-born, presumed female Hoffmann's two-toed sloth (Choloepus hoffmanni) presented in respiratory distress with severe dehydration and symptoms of hypotension. During treatment, dysphagia was noted and oral examination revealed enlarged palatine tonsils and mucosal plaques. Bloodwork showed a decreased sodium:potassium ratio, a low baseline cortisol, a decreased adrenocorticotropin response test, and a blunted aldosterone stimulation test. All values were compared to a healthy male Hoffmann's two-toed sloth at the same facility. Despite aggressive medical management and treatment for hypoadrenocorticism, the sloth was found deceased. Necropsy revealed abdominal effusion, multifocal plaques throughout the upper gastrointestinal tract, and testes. Histopathology showed marked adrenal cortical atrophy and intranuclear mucosal inclusions in the gastrointestinal tract; advanced molecular techniques did not uncover any viral etiologies. This is the first reported case of hypoadrenocorticism in a sloth.