Objective To systematically review the relationship between preoperative platelet-to-lymphocyte ratio (PLR) and prognosis in patients with pancreatic ductal adenocarcinoma (PDAC). Methods Studies on the relationship between preoperative PLR and prognosis of PDAC patients were retrieved from China National Knowledge Infrastructure, Chongqing VIP, SinoMed, Wanfang, PubMed, Embase, Web of Science, and Cochrane Library, with a search period from databases establishment to December 2023. A meta-analysis was conducted using RevMan 5.3 software. Results A total of 7 studies were included, including 1273 patients. The meta-analysis results showed that the postoperative overall survival [hazard ratio (HR)=1.69, 95% confidence interval (CI) (1.24, 2.30)] and disease-free survival [HR=1.83, 95%CI (1.49, 2.24)] of PDAC patients with high preoperative PLR were shortened (P<0.05). The results of subgroup analysis showed that when the cut off of PLR was<200, preoperative high PLR was associated with shortened overall survival (HR=1.91, P<0.05), but when the cut off of PLR was ≥200, there was no significant correlation between preoperative PLR and overall survival (P>0.05). When followed up for<3 years, preoperative high PLR was associated with shortened overall survival (HR=2.05, P<0.05), but when followed up for ≥3 years, there was no significant correlation between preoperative PLR and overall survival (P>0.05). Conclusion Current evidence suggests that preoperative high PLR may be a risk factor for poor prognosis in PDAC patients.