The main differentials in cases of sudden elevation of hepatic enzyme levels during immunochemotherapy are reactivation of hepatitis B virus or drug-induced liver injury. Here, we report a case of acute liver injury caused by hepatitis E virus (HEV) during chemotherapy for malignant lymphoma, wherein the patient was successfully treated and completed chemotherapy. A 57-year-old woman visited her local doctor because she felt light and tired. The patient underwent lower gastrointestinal endoscopy and was diagnosed with a malignant lymphoma of the small intestine (diffuse large B-cell lymphoma). The patient had a history of oral consumption of undercooked pork liver to improve anemia and was diagnosed with acute hepatitis E. Since the patient responded to chemotherapy, she was treated with single-agent ribavirin while continuing chemotherapy, resulting in a sustained virological response. Even during treatment with immunosuppressive drugs, if appropriate treatment for hepatitis E can be administered, the patient can be fully treated without interruption. The patient was able to complete chemotherapy adequately without interruption of treatment, which was a clinically beneficial result.