Surgical site infection (SSI) is a well-known complication in older adults. However, there have been no studies on SSI after gastrectomy in older adults. Therefore, we aimed to investigate the incidence, risk factors, and outcomes of SSIs after gastrectomy in older adults.We performed a retrospective cohort study of older adults, aged 65 years or older, who underwent gastrectomy between January 2015 and December 2015 at the Severance Hospital in Seoul, Korea. The incidence and outcomes of SSIs after gastrectomy were evaluated, and the risk factors for SSI were identified using multivariate analyses.We identified 353 older adults who underwent gastrectomy. Of these, 25 patients (7.1%) developed an SSI. Multivariate analysis indicated that open surgery (odds ratio, 2.71; 95% confidence interval, 1.13-6.51; P = .03) and a longer operation time (odds ratio, 1.01; 95% confidence interval, 1.00-1.01; P = .04) were independent risk factors for SSI after gastrectomy. In the SSI group, the incidence of postoperative fever (84.0% vs 51.8%; P < .001), length of postoperative hospital stay (13 days vs 6 days; P < .001), and re-admission rates within 30 days postoperatively (32.0% vs 3.4%; P < .001) were significantly higher than those in the non-SSI group.The risk factors for SSI in older adults after gastrectomy were open surgery and a longer operation time. When an SSI occurred, the postoperative hospital stay was prolonged and the chances of having a postoperative fever and being re-admitted within 30 days increased.