Adult T-cell leukemia÷lymphoma (ATL) is caused by human T-cell lymphotropic virus type-1 (HTLV-1) infection. Classification of ATL includes acute, chronic, lymphomatous and smoldering, and main features are hypercalcemia, organomegaly, bone, brain, lung, and skin changes. Elevated mortality rates of ATL may be due to the advanced age at diagnosis, because this malignancy can evolve unsuspected for decades before the first clinical manifestations. Palliative therapy, chemotherapy and stem cell transplantation are often utilized, but response to treatment is poor. The patient herein reported presented diffuse abdominal pain with duration of eight months in addition to ascites. The diagnosis of the acute leukemia type of ATL was done with base on clinical, laboratory and imaging findings. Gastrointestinal symptoms and ascites are uncommon first manifestations of ATL, and pose challenging diagnosis.