We report a case of a 6-month-old boy with a mixed phenotype acute leukemia (MPAL), bilineal and biphenotypic immunophenotype (B-lymphoid lineage and combined B-lymphoid and monocytic lineage) with t(10;11)(p12;q23);. MLL-MLLT10. He was treated with acute myeloid leukemia protocol and in complete remission at 7-month follow-up. To the best of our knowledge, this is the first reported MLL-MLLT10 rearranged case presenting as MPAL in an infant. From a clinical practice standpoint, this case illustrates the importance of detection of MLL rearrangement due to its prognostic implication and the effectiveness of flow cytometry immunophenotyping in diagnosing MPAL and monitoring minimal residual disease. © 2010 Elsevier Ltd.