Postoperative complications of gastrectomy for gastric cancer affect the efficacy of surgery. It is of clinical significance to identify high-risk patients with postoperative complications as early as possible. A total of 206 patients who underwent gastrectomy were enrolled in this study. Univariate and multivariate analyses were used to determine the risk factors for postoperative complications. The cutoff value and diagnostic accuracy of the C-reactive protein/albumin ratio were calculated by receiver operating characteristic curves. A total of 64 (31.1%) patients developed postoperative complications. Multivariate analysis confirmed that the C-reactive protein/albumin ratio on the first day after operation was an independent risk factor for postoperative complications (OR = 2.538, 95%CI: 1.346-4.785, P = 0.004). The cutoff value of the C-reactive protein/albumin ratio on the first day after operation was 2.105 calculated by receiver operating characteristic curves. Patients with a C-reactive protein/albumin ratio greater than 2.105 had a higher incidence of postoperative complications (43.2% vs 22.0%, P = 0.001) and longer postoperative hospital stay (15.3 ± 1.2 vs 13.0 ± 0.5, P = 0.042) than patients with less than 2.105. Patients with C-reactive protein/albumin ratio greater than 2.105 on the first day after operation are more likely to have postoperative complications.