This study retrospectively investigated the prognostic impact of the geriatric nutritional risk index (GNRI) in colorectal cancer (CRC). This study reviewed the medical records of 329 CRC patients who underwent curative surgery. The GNRI was calculated from the serum albumin level and the body weight. The cutoff value for the GNRI was set at 98. One hundred ninety (57.8%) patients had a GNRI of ≥98, and 139 (42.9%) had a GNRI of <98. The patients with a lower GNRI had a significantly lower overall survival (OS) rate than those with a higher GNRI (p < 0.001). The multivariate analysis demonstrated that the GNRI was an independent predictor of the OS (p = 0.042). Non-cancer death was more frequent in the patients with a lower GNRI than in those with a higher GNRI (p = 0.003). The mean age was significantly higher in the patients with a lower GNRI (p < 0.001). The GNRI was significantly associated with tumor location (p = 0.048), tumor depth (p < 0.001) and carcinoembryonic antigen (CEA) level (p = 0.032). The GNRI is a simple and useful prognostic factor in CRC. The present study suggests that a low GNRI be associated with a higher risk of non-cancer death.