Preliminary: Chronic myeloid leukaemia (CML) is a clonal hematopoiesis stem cell disorder, characterised by reciprocal translocation between chromosomes 9 and chromosomes 22, originally named the ?Philadelphia chromosome?(Ph). The megakaryoblastic transformation of a CML is extremely rare, consisting <3% of transformed cases. Case description: A 68-year-old male presented with a CML history since 2000 and received Imatinib therapy. The patient currently showed anemia and splenomegaly. Laboratory results showed hemoglobin 8.1 g/dL, leukocyte count 31,740/?L, platelet count 7,000/?L, Immature Platelet Fraction (IPF) 29.2%, BCR-ABL gene fusion is positive. Bone marrow examination showed CML blastic crisis phase with 45% blasts which had megakaryoblast morphology so it was concluded as a CML that underwent a transformation into megakaryoblastic. The results of bone marrow aspirate using Sysmex-XN1000 showed a very high IPF value which indicated an increased megakaryopoietic proliferative activity. Immunophenotyping examination showed blast population with CD45 dim, low side scatter, with the expression of CD34+, CD33+, CD13+ corresponding to the megakaryoblast area. Examination of the CD41 and CD61 specific megakaryoblast markers was not performed due to reagent limitations. Discussion: Clinical features, morphology, immunophenotyping and molecular findings help the identification of CML with suspected megakaryoblastic transformation. Conclusion: A CML patient has been reported with suspected megakaryoblastic transformation based on the bone marrow morphology, immunophenotyping, molecular and elevated IPF examination.