Inflammation and immunity have an important role in the development of cancer. The lymphocyte-to-monocyte ratio (LMR) has been shown to be of prognostic value in several malignant forms. The purpose of this study was to analyze the prognostic significance of preoperative LMR in post-curative resection of pancreatic adenocarcinoma.A total of 144 patients with primary pancreatic adenocarcinoma who underwent curative operation were enrolled in this retrospective study. The correlation between preoperative LMR and survival was analyzed using Kaplan-Meier curves and multivariate Cox regression analyses.In the univariate analysis, an elevated preoperative LMR was significantly associated with an increased overall survival (OS) (19 months vs 12 months, P=0.000), and this result remained significant in the multivariate analysis (hazard ratio [HR]: 0.148; 95% confidence interval [CI]: 0.085-0.252; P=0.000). Furthermore, patients with high LMR also had higher median recurrence-free survival (RFS) than patients with low LMR in univariate (18 months vs 10 months, P=0.000) and multivariate analyses (HR: 0.148; 95% CI: 0.085-0.252; P=0.000). Subgroup analyses showed that both patients with stage III cancer and patients with stage I+II cancer can obtain OS and RFS benefits from high LMR.LMR can be considered as an independent prognostic biomarker for operable pancreatic adenocarcinoma.