The global incidence of colorectal cancer (CRC) in patients receiving hemodialysis is steadily rising. However, current information on the clinical use of chemotherapy for patients undergoing hemodialysis with CRC is limited. Herein, we describe a clinical course of a 74-year-old patient undergoing hemodialysis with unresectable CRC treated with folinic acid, 5-fluorouracil (5FU), and irinotecan (FOLFIRI) plus bevacizumab whose changes in serum bevacizumab concentration were analyzed. Treatment was initiated with a standard dosage of 5-FU and 80% of the standard dose of irinotecan to avoid any adverse events. However, neutropenia (grade 4) was observed after five treatment cycles, which prompted a dose reduction of 5-FU and irinotecan, after which treatment was safely completed. Progression-free survival of the patient was 7.5 months. Changes in serum bevacizumab concentration were similar to those documented in patients with normal renal function. In addition, no bevacizumab-related adverse events occurred. It was inferred that FOLFIRI plus bevacizumab therapy could be implemented as a safe and efficient treatment for patients undergoing hemodialysis with unresectable CRC. To the best of our knowledge, this is the first report of the analysis of serum bevacizumab concentrations in a patient undergoing hemodialysis with unresectable CRC.