We present a patient with Epstein-Barr virus (EBV)-positive cytotoxic peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) who was successfully treated using only L-asparaginase. A 46-year-old Japanese man was diagnosed with EBV-positive cytotoxic PTCL-NOS. Although he underwent chemotherapy using multiple agents, he relapsed with hemophagocytic syndrome. L-asparaginase treatment was initiated at 6,000 U/m(2) on days 1, 3, 5, 10, and 12 together with prednisolone at 1 mg/kg. Although he developed grade 2 liver dysfunction and grade 2 coagulopathy, the patient achieved complete response status. Finally, he underwent allogeneic bone marrow stem cell transplantation, and he is currently still alive without disease at 24 months after the start of L-asparaginase therapy.