A 45-year-old man with chronic active Epstein-Barr virus (EBV) infection (CAEBV) with natural killer cell type developed pulmonary arterial hypertension (PAH). After chemotherapy, he showed marked depression of the EBV DNA genome in the peripheral blood, but PAH sustained. He died of heart failure due to PAH, and the histo-pathological examination revealed pulmonary vascular abnormalities without lung disease on autopsy. Although the EBV DNA genome and the infiltrating lymphocytes were not detected in the lung, his clinical course suggested that his PAH might be caused by CAEBV. This is the first reported case of PAH associated CAEBV in an adult.