Although the classic t(8;21) has been reported in 10 pediatric patients with acute myeloid leukemia with eosinophilia (AML M4Eo), no complex variant t(8;21) in children with AML M4Eo has been previously described. In our analysis of leukemic blasts from a 4-year-old boy with AML M4Eo, conventional cytogenetics revealed that 95% of the cells had a hypodiploid line containing 45 chromosomes and a complex karyotype involving chromosomes 3, 8, and 21. Fluorescence in situ hybridization using whole chromosome painting probes for these chromosomes confirmed the cytogenetic findings. The presence of a CBFA2-ETO fusion gene was established by fluorescence in situ hybridization and reverse-transcriptase polymerase chain reaction analysis. Thus, this report illustrates the first description of a complex variant t(8;21) involving chromosome band 3q27 in a child with AML M4Eo.