The prognosis for relapsing or refractory neuroblastoma (NB) remains dismal, with a five-year disease-free survival of <20%, and no effective salvage treatment has been identified so far. I-131-metaiodobenzylguanidine (I-131-MIBG) has come to play an essential role in the imaging and therapy of NB over the past 30 years. The role of I-131-MIBG in the treatment of NB is continually expanding. I-131-MIBG treatment together with cumulative doses of other alkylating agents has potential serious late side effects such as myelodysplasia and leukemia, although rare. We describe a secondary acute myeloid leukemia case with complex karyotypic anomalies that included monosomy 5, monosomy 7 and translocation (1;10) in a child with relapsed NB who received therapeutic I-131-MIBG.