Background: Elderly patients are often intolerable in combination of cytotoxic agents. Recently, Trifluridine/tipiracil plus bevacizumab has been shown as good candidate for the vulnerable patients. We aimed to assess the efficacy and safety of trifluridine/tipiracil plus bevacizumab in elderly patients with metastatic colorectal cancer. Methods: Patients aged 70 years and older with previously untreated, unresectable, metastatic colorectal cancer, who were not deemed to be candidates for oxaliplatin-based or irinotecan-based chemotherapy regimens, were included in this trial. Treatment consisted of trifluridine/tipiracil (35 mg/m² orally a day on day 1-5 and day 8-12) with bevacizumab (5mg/kg intravenously on day 1 and day 15), given every 4 weeks until disease progression. The primary endpoint was progression-free survival (PFS). The secondary endpoints were response rate (ORR), Overall survival (OS) and adverse events (AEs). Results: Between 2017 January and 2018 March, 39 patients were enrolled in this study. The characteristics of patients were male/female : 17/22, median age : 77.5 (range: 70-88) and PS: 0/1 : 31/8. The ORR of 37 patients were assessed by the central review committee. The best response was 40.5(15/37) % (95% CI: 24.8-57.9), and the disease control rate was 86.5 (32/37) % (95% CI: 71.2–95.5). The AEs which were frequent as grade 3 or 4 were leucopenia (71.8 %), neutropenia (48.7 %), anorexia (12.8 %), febrile neutropenia (10.3 %) and fatigue (10.3 %). No treatment related death was reported. Conclusions: The combination of trifluridine/tipiracil plus bevacizumab is an effective and well-tolerated regimen for elderly patients with metastatic colorectal cancer. Hematological adverse events were need for caution. The primary endpoint of PFS will be presented in the end of this year. Clinical trial information: UMIN000025241.