We reported 2 cases of hepatic encephalopathy after chemotherapy for advanced colorectal cancer. Case 1: A 49-year-old male was diagnosed advanced sigmoid colon cancer with peritoneal dissemination, multiple liver metastasis and multiple osseous metastasis. After resection of primary lesion, we administered mFOLFOX6 plus bevacizumab combination therapy. He was in comatose(Japan coma scale 200)3 days after 2 courses of administration of this regimen. Case 2: A 57-year-old female was diagnosed advanced rectal cancer with multiple huge liver metastasis and multiple osseous metastasis. We administered mFOLFOX6 plus panitumumab combination therapy. She was in comatose(Japan coma scale 100)3 days after 10 courses of administration of this regimen. In both cases, radiographic imaging showed no abnormal sign and blood examination revealed a high level of serum ammonia. We diagnosed their disturbance of consciousness as a symptom of hepatic encephalopathy. Branched-chain amino acid infusion rapidly improved disturbance of consciousness. We must consider the symptom, hepatic encephalopathy in patients receiving chemotherapy for advanced colorectal cancer.