Solid tumors may occur in 3% of the patients with chronic myeloid leukemia (CML). Philadelphia (Ph)-positive CML was diagnosed in a 66-year-old man upon a white blood cell count of 58.1 × 109/L. He had no symptoms and physical findings 3 years after treatment for rectal adenocarcinoma. Imatinib mesylate 400 mg/day was started and white blood cell count was lowered to 5.7 × 109/L in 1 month. The patient had received several chemotherapeutic agents such as 5-fluorouracil, irinotecan, raltitrexed, capecitabine, and oxaliplatin. In the literature, there are two reports on CML after the treatment of colorectal carcinoma. The possibility of a relationship between oxaliplatin and/or irinotecan and CML may not be fully excluded. In conclusion, hematological disorders such as CML may emerge in colorectal carcinoma and whole blood counts should be carefully checked. The possibility of a relationship between CML and the chemotherapeutic agents in colorectal carcinoma should be further evaluated.