Chronic neutrophilic leukemia (CNL) is a rare myeloproliferative neoplasm (MPN) characterized by persistent peripheral blood neutorphilia, bone marrow hypercellularity of neutrophilic granulocyte proliferation and hepatosplenomegaly. Acquired somatic mutation, JAK2 V617F, is the only molecular marker known to have association with classic BCR-ABL1 negative MPNs. However, JAK2 V617F has been detected occasionally in other MPNs such as CNL or other disease entities. We experienced a case of CNL with JAK2 V617F mutation. The patient was diagnosed according to the 2008 WHOclassification criteria, and developed AML 9 months after the diagnosis of CNL. The JAK2 V617F was detected in the bone marrow throughout the clinical course. More cases are needed to establish the role of JAK2 V617F in the pathogenesis, prognosis and diseasecourse of CNL.