Imatinib mesylate is a tyrosine kinase inhibitor used to treat various oncological conditions, such as chronic myeloid leukemia. It is generally well tolerated with some cutaneous side effects. The most frequent dermatological side effect is hypopigmentation, but paradoxical hyperpigmentation has been rarely reported. Especially, imatinib-induced acquired dermal melanocytosis has been reported very rarely in the English literature. A 48-year-old woman with chronic myeloid leukemia presented with bluish to brownish macules and patches at face, upper trunk, and buttock. She had been treated with imatinib for 9 years, and the facial lesion began to occur 3 months after treatment. During the recent 2 years, the lesions have been developed at trunk and buttock. Histological examination of the lesion revealed the presence of a dendritic and stellate-shaped dermal melanocytes. Immunohistochemically, these cells were positive for melan-A, fontana silver and S-100. Based on these clinicopathological findings, she was diagnosed with acquired dermal melanocytosis induced by imatinib mesylate. The exact mechanism of imatinib-induced paradoxical hyperpigmentation is unclear. It has been hypothesized that it could have different target effects on immature and mature melanocytes and KIT and its ligand stem cell factor (SCF) play a critical role in the pathogenesis. Herein, we report a rare case of imatinib-induced acquired dermal melanocytosis.