Multiple RBC transfusions inevitably lead to a state of iron overload before and after high-dose chemotherapy and autologous stem cell transplantation (HDCT/autoSCT). Nonetheless, iron status during post-SCT follow-up remains unknown. Therefore, we investigated post-SCT ferritin levels, factors contributing to its sustained levels, and organ functions affected by iron overload in 49 children with high-risk neuroblastoma who underwent tandem HDCT/autoSCT. Although serum ferritin levels gradually decreased during post-SCT follow-up, 47.7% of the patients maintained ferritin levels above 1,000 ng/mL at 1 yr after the second HDCT/autoSCT. These patients had higher serum creatinine (0.62 vs 0.47 mg/mL, P = 0.007) than their counterparts (< 1,000 ng/mL). Post-SCT transfusion amount corresponded to increased ferritin levels at 1 yr after the second HDCT/autoSCT (P < 0.001). A lower CD34(+) cell count was associated with a greater need of RBC transfusion, which in turn led to a higher serum ferritin level at 1 yr after HDCT/autoSCT. The number of CD34(+) cells transplanted was an independent factor for ferritin levels at 1 yr after the second HDCT/autoSCT (P = 0.019). Consequently, CD34(+) cells should be transplanted as many as possible to prevent the sustained iron overload after tandem HDCT/autoSCT and consequent adverse effects.