A woman in the 70s with a decreased appetite and weight loss (4 kg) in the last 3 months was referred to our hospital. An enhanced CT scan of the abdomen showed a hepatocellular carcinoma (HCC) of 83 mm in diameter of the liver with metastasis to the para-aortic lymph nodes, the left adrenal gland, and the right lower lung lobe (cStage IVb). She was started on atezolizumab + bevacizumab (Atezo-Bev) therapy. A week after the treatment, she began to have a decreased appetite, fever in the 39 °C range, subcutaneous bleeding, and a slight headache when walking. So she was urgently admitted to our hospital. We diagnosed her as having a hemophagocytic syndrome and administered 1 g steroid pulse therapy for 3 days followed by 1 mg/kg of prednisone. Her condition began to improve. This is the first case report of a hemophagocytic syndrome in a patient with HCC treated with Atezo-Bev.