IgA nephropathy (IgAN) is one of the most frequent forms of glomerulonephritis (GN). However, its association with polycythemia vera (PV) has rarely been described. We report a case of IgAN combined with PV. The patient was a 46-year-old male with chronic renal failure, heavy proteinuria and erythrocytosis. He also presented hypertension and hematuria as well as splenomegaly, high arterial oxygen saturation and elevated leukocyte alkaline phosphatase activity. Possible causes of secondary erythrocytosis were ruled out. The renal biopsy revealed mesangial proliferative GN with predominant IgA deposition in mesangium. He was diagnosed as having IgAN and PV concomitantly. After administration of hydroxyurea, enalapril and felodipine, blood cell count and blood pressure normalized, while azotemia persisted. There was also a partial remission of the heavy proteinuria. We describe a case of IgAN associated with PV, and possible pathophysiologic relationships between two diseases are discussed with review of the literature.