Objective The immune inflammation-based score is recognized as a prognostic marker for cancer. However, the most accurate prognostic marker for patients with gastric cancer remains undetermined. We aimed to evaluate the predictive value of the lymphocyte-to-C-reactive protein ratio for outcomes in gastric cancer patients after radical gastrectomy. Methods A total of 607 gastric cancer patients treated at three Chinese institutions were included. Receiver operating characteristic curves were generated, and the areas under the curve were calculated to compare the predictive value among the inflammation-based score, lymphocyte-to-C-reactive protein ratio, C-reactive protein/albumin and neutrophil-lymphocyte, platelet-lymphocyte and lymphocyte-monocyte ratios. Cox regression was performed to determine the prognostic factors for overall survival. Results The median follow-up time was 63 months (range: 1–84 months). The optimal cut-off value for lymphocyte-to-C-reactive protein ratio was 0.63. The patients were divided into the LCR <0.63 (LLCR, n = 294) group and the LCR ≥0.63 (HLCR, n = 313) group. LLCR was significantly correlated with poor clinical characteristics. Compared with inflammation-based score, lymphocyte-to-C-reactive protein ratio had the highest areas under the curve (0.695). Patients with LLCR experienced more post-operative complications than the HLCR group (20.4 vs. 12.1%, P = 0.006). Multivariate analysis showed that a higher lymphocyte-to-C-reactive protein ratio (HR: 0.545, 95%CI: 0.372–0.799, P = 0.002) was associated with better overall survival. The HLCR group had higher 5-year overall survival rate than the LLCR group (80.5 vs. 54.9%, P < 0.001). Conclusions Preoperative lymphocyte-to-C-reactive protein ratio levels can effectively predict the short-term and oncological efficacy of gastric cancer patients after radical gastrectomy with a predictive value significantly better than other inflammation-based score.