Hypereosinophilic syndrome (HES) is a clinical disorder characterized by persistent eosinophilia and systemic involvement, in which a specific causative factor for the eosinophilia cannot be verified during a certain period of time. There have been only a few reported cases of this syndrome associated with malignant lymphoma. We report a case of peripheral T-cell lymphoma-unspecified with hypereosinophilic syndrome. The patient was a 42-year-old woman with an uncontrolled fever and a sore throat. Eosinophilia was observed on the peripheral blood smear. We confirmed the diagnosis by bone marrow and liver biopsies:. A bone marrow aspiration demonstrated markedly increased eosinophils (24.8%), and a liver biopsy demonstrated infiltration by scattered eosinophils and atypical lymphoid cells, which were confirmed to be T-cell lymphoma cells. This case was a distinctive presentation of peripheral T-cell lymphoma with hypereosinophilic syndrome, probably due to a paraneoplastic condition.