Chronic infection with Epstein-Barr virus (EBV) without previous immunodeficiency or immuno-suppressive therapy is relatively rare. Severe chronic active EBV (SCAEBV) infection was reported for the first time in 1984 as 'chronic mononucleosis syndrome', and diagnostic criteria were proposed. It is characterized by clinical features including fever, severe hepatosplenomegaly, lymphadenopathy, hematologic features such as anemia and thrombocytopenia, and elevated antibody titers to EBV. We experienced a 21-year-old woman who initially presented with fever and chronic fatigue; however, no definite diagnosis could be made at the time of admission. Three months after the initial admission, there was evidence of only splenomegaly and the patient had persistent, multiple, paraaortic lymphadenopathies in abdominal CT. Diagnostic splenectomy was performed, and SCAEBV infection with T-cell lymphoproliferative disorder was ultimately diagnosed.