Although the effectiveness of trifluridine/tipiracil(TFTD)with bevacizumab for unresectable colorectal cancer that was refractory to previous standard chemotherapy was reported, its effectiveness as a first-line treatment, especially for elderly frail patients, is unclear. An 85-year-old woman complaining of anorexia was diagnosed with unresectable sigmoid colon cancer with multiple metastases. Her general status was very poor, and her performance status(PS)was 4. We first performed laparoscopic transverse colostomy. As her general status gradually improved, we administered TFTD with bevacizumab as a first-line treatment based on the patient's strong request for chemotherapy. The patient underwent this regimen in the outpatient clinic for 9 months(9 courses). Although the size of the liver metastases increased, lung metastases and abdominal disseminations were under control and her PS became 0. She has been taking mFOLFOX6 with bevacizumab (80%)as a second-line treatment. TFTD with bevacizumab treatment was safe and efficacious as a first-line treatment for a frail elderly patient with unresectable colorectal cancer.