Adult T cell Leukemia/lymphoma (ATL) is a mature T-cell neoplasm that has strong association with the human T-lymphotropic virus type 1 (HTLV-I) infection. This infection is endemic in our region (north eastern Iran). It has been highlighted that Janus Kinase family proteins and specially JAK2 mutations have a pivotal role in the development of many types of hematological malignancies and in particular myeloproliferative neoplasms. So far, the underlying molecular mechanisms leading to the ATL are not well understood. Therefore, in this study it was hypothesized that JAK2 (V617F) mutation may be present in samples from patients with ATL. This case control study was performed in north-eastern Iran. Using polymerase chain reaction, JAK2 (V617F) mutation was performed in 20 DNA samples from ATL patients and 20 HTLV-1 asymptomatic carriers (control group). The results of ATL subjects and the control group were compared by using SPSS software. In the case group 13 (65 %) and 7 patients (35 %) were male and female respectively, with the age range between 40 and 80 years. Only one patients has JAK2 mutation and this mutation was absent in 95 % of ATL patients as well as the HTLV-1 asymptomatic carriers. The results of our study demonstrated that JAK2 V617F mutation is not a common phenomenon in ATL. However, further studies are required to investigate the possible dysregulation of JAK signaling in ATL.