Visceral leishmaniasis (VL) or Kala-azar is a common parasitic infection among children in Iran. The records of 249 children with VL were evaluated retrospectively. The clinical, hematologic, and bone marrow biopsy findings were studied. In particular, we assessed whether there was an association between bone marrow biopsy findings and prognosis. Five major groups were identified: (1) hypercellular marrow with many Leishman Donovan (LD) bodies, (2) multiple noncaseating granulomas with a few LD bodies, (3) diffuse fibrosis with rare LD bodies, (4) benign lymphoid nodules with many LD bodies, and (5) marrow necrosis with many LD bodies. The patients with hypercellular marrow and benign lymphoid nodules were alive and responded well to glucantime therapy. The patients with marrow fibrosis and marrow necrosis died and were resistant to any type of therapy. Patients with granulomas did not respond to glucantime therapy but responded to amphotericin B. However, less than half of the patients died owing to malnutrition and misdiagnosis. We correlated the bone marrow biopsy findings with the treatment outcomes and prognosis. The outcome was excellent in cases of hypercellular marrow, very poor in cases of fibrosis and necrosis, and intermediate in cases of granulomas. As a result, we believe that bone marrow biopsy findings can be helpful for assessing the prognosis of VL patients.