A 67-year-old man with elevated serum immunoglobulin G4 (IgG4) levels, systemic lymphadenopathy infiltrated by IgG4-positive plasma cells, and Coombs-positive autoimmune hemolytic anemia (AIHA) showed marked hypercalcemia. Although the intact parathyroid hormone (PTH) level was elevated, 99mTc-MIBI scintigraphy and thyroid ultrasonography revealed no evidence of primary hyperparathyroidism. Liver biopsy showed marked infiltration of IgG4-positive plasma cells, which confirmed the diagnosis of IgG4-related disease (IgG4-RD). Corticosteroid therapy was initiated, and subsequently, intact PTH and serum calcium levels gradually normalized. Transient hypercalcemia in a patient with AIHA may therefore be associated with IgG4-RD.