Long-term outcomes in gastric cancer patients with positive lavage cytology (CY1) are generally poor. This multi-institutional retrospective cohort study aims to evaluate the clinical significance of the neutrophil-lymphocyte ratio (NLR) and the lymphocyte-monocyte ratio (LMR) in CY1 gastric cancer patients. A total of 121 CY1 gastric cancer patients without other non-curative factors, who underwent macroscopically curative resection, were enrolled in this study. The cutoff values of preoperative NLR (pre-NLR), postoperative NLR (post-NLR), preoperative LMR (pre-LMR), and postoperative LMR (post-LMR) were defined by the Contal and O'Quigley method as 2.3, 3.0, 2.5, and 3.2, respectively. A Cox proportional hazard model was used to identify the independent prognostic factors among NLR, LMR, and other clinicopathological factors. There were significant differences in the overall survival (OS) between the two groups: high post-NLR groups vs. low post-NLR group (median survival time, months) (10.9 vs. 22.8, P = 0.006) and high pre-LMR group vs. low pre-LMR group (21.3 vs. 11.0, P = 0.001). The LMR value elevated significantly after gastrectomy (P = 0.020), although not in the NLR value (P = 0.733). On multivariate analysis, high post-NLR (hazard ratio = 1.506; 95% confidence interval = 1.047-2.167; P = 0.027), low pre-LMR (1.773; 1.135-2.769, 0.012), and no postoperative chemotherapy (1.558; 1.053-2.305, 0.027) were found to be independent prognostic factors for adverse OS. Because a combination of high post-NLR and low pre-LMR may be an adverse prognostic marker in resectable CY1 gastric cancer patients, it is necessary to conduct a prospective trial to confirm a useful perioperative chemotherapeutic regimen for these patients.