The concomitant presence of the XYY syndrome with haematological malignancies is rare. This report presents a case of acute promyelocytic leukaemia (APL) with the promyelocytic leukaemiaretinoic acid receptor alpha (PML-RARA) gene insertional translocation and a chromosome 21 abnormality in a 29-year-old XYY male patient. Karyotype analysis revealed an abnormal karyotype of 47,XYY [14]/46,XYY,-21 [16]. Fluorescence in situ hybridization and reverse transcriptionpolymerase chain reaction analysis showed the existence of a PML-RARA fusion gene. The patient was treated by all-trans retinoic acid (ATRA) and chemotherapy. Laboratory results revealed that the coagulopathy improved and the patient achieved complete remission, based on bone-marrow morphology. The patient then received sequential monthly therapy using arsenic trioxide, followed by ATRA, followed by chemotherapy; he has survived disease-free for 36 months. Our findings suggest that the additional chromosomal abnormalities involving the sex chromosomes and chromosome 21 did not affect the prognosis of APL, and that the sequential treatment strategy had a good clinical effect without being associated with severe side-effects.