BackgroundThe geriatric nutritional risk index (GNRI) is a simple nutritional and inflammatory marker for older adults. The aim of the present study was to investigate the usefulness of the GNRI in older adults who underwent emergency gastrointestinal surgery.MethodsThis study included 206 older adults who had undergone emergency gastrointestinal surgery. We retrospectively investigated the relationship between the GNRI and postoperative complications. Univariate and multivariate analyses were performed to evaluate risk factors for postoperative complications. We then evaluated the association between GNRI and clinical variables among older adults undergoing emergency gastrointestinal surgery.ResultsPostoperatively, all complications occurred in 89 (43%) older adults, infectious in 53 (26%), and non‐infectious in 36 (17%). In the multivariate analysis, age (p = 0.016), GNRI (p = 0.012), operative severity (p = 0.003), and operation time (p = 0.003) were independent risk factors for all postoperative complications. While the GNRI (p = 0.049) was an independent risk factor for infectious complications, age (p = 0.035) and bleeding volume (p = 0.035) were independent risk factors for postoperative non‐infectious complications. In the low GNRI group, age (p = 0.029), serum C‐reactive protein levels (p < 0.001), and proportion of sarcopenia (p < 0.001) were significantly higher, and the length of hospital stay (p < 0.001) was significantly longer than that in the high GNRI group. In Spearman's rank correlation coefficient, the skeletal mass index and the GNRI had a positive correlation (r = 0.415 and p < 0.001).ConclusionThe GNRI may be a predictor of postoperative infectious complications in older adults after emergency gastrointestinal surgery, suggesting the usefulness of the GNRI as a nutritional marker and sarcopenia‐related parameter.Trial registration numberNo. 22‐16.