Chronic myeloid leukemia (CML) is one of the myeloproliferative neoplasms whose incidence peaks in older individuals and is characterized by the uncontrolled proliferation of cells in the myeloid cell line. It can present with symptoms related to leukocytosis or splenomegaly, and it can also be asymptomatic and found incidentally. Nilotinib is a second-generation tyrosine kinase inhibitor used in the treatment of the chronic phase of CML and was found to cause diabetes mellitus among other adverse effects. These adverse effects seem to occur after a few months to a few years of drug administration. Type-two diabetes is the most common type of diabetes; its hallmark being insulin resistance with resultant hyperglycemia. Most often, it has no symptoms and is usually found as an incidental finding or on screening. Here we present a 45-year old Chinese female, who was diagnosed with CML chronic phase after an incidental finding of leukocytosis; treated with nilotinib as upfront for CML, and developed diabetes mellitus after about one and a half years of treatment, which was treated with metformin.