Renal involvement by leukemic cells is rare in chronic myelogenous leukemia (CML). Herein, this study reports a case of CML associated with renal involvement of leukemic cells, which occurred 1 and 1/2 years after the initial diagnosis. Abdomino-pelvic computed tomography revealed a 4.4 × 4.2 cm-sized, low-density solid mass having a thick wall from the mid to lower pole of the left kidney. A peripheral blood analysis revealed blastic transformation of CML. The biopsied renal parenchyme was diffusely infiltrated by sheets of immature myeloid cells, polymorphonuclear leukocytes, and occasional eosinophils. Most of the infiltrating cells were positive for anti-neutrophil elastase, but negative for lymphoid markers. Therefore, differential diagnosis of a kidney tumor during the course of CML, especially in the time of blastic transformation, should be performed.