Rationale:Hypercalcemia is a common complication of many granulomatous diseases but is not typically associated with leishmaniasis. Here we report an unusual case of hypercalcemia during the initiation of antiviral therapy in a patient with acquired immunodeficiency syndrome coinfected with visceral leishmaniasis.Patient Concerns:Our patient presented with malaise and altered mental status following antiretroviral therapy initiation. He was found to have de novo hypercalcemia complicated by acute kidney injury.Diagnosis, interventions, and outcomes:An extensive workup for other etiologies of hypercalcemia was negative. The patient was ultimately thought to have hypercalcemia secondary to visceral leishmaniasis in the setting of immune reconstitution inflammatory syndrome. He was treated with intravenous volume expansion, bisphosphonates, and oral corticosteroid therapy with complete resolution.Lessons:This case highlights an unusual presentation of immune reconstitution inflammatory syndrome, in which proinflammatory cytokine signaling during the restoration of cellular immunity may have led to increased ectopic calcitriol production by granuloma macrophages, thereby altering bone-mineral metabolism and driving hypercalcemia.