CASE DESCRIPTION Primary hypoaldosteronism without concurrent hypoadrenocorticism was diagnosed in an 8-year-old female alpaca with acute onset of weakness progressing to recumbency within 6 hours after onset. CLINICAL FINDINGS Hematologic testing at admission revealed profound hyponatremia, hypochloremia, and acidemia with a normal blood potassium concentration. Further diagnostic testing, including an ACTH stimulation test, led to a diagnosis of hypoaldosteronism in conjunction with normal cortisol production. TREATMENT AND OUTCOME The hembra responded well to i.v. polyionic fluid therapy with sodium supplementation and was managed successfully long term with free access to saline (0.9% NaCl) solution in addition to water ad libitum. CLINICAL RELEVANCE To our knowledge, this is the first reported case of hypoaldosteronism in an alpaca. Hypoaldosteronism should be considered in alpacas as a possible differential diagnosis for refractory hyponatremia or for hyponatremia in which an underlying etiology is not determined.