Introduction <p>Systemic inflammatory response (SIR) indicators serve as predictive factors for lymph node metastasis (LNM) in various cancers. This study aimed to investigate the association of platelet-to-lymphocyte ratio (PLR) and neutrophil-to-lymphocyte ratio (NLR) with LNM in rectal cancer and to identify clinicopathological factors linked to LNM.</p> Methods <p>We retrospectively analyzed 181 rectal cancer patients who underwent surgical resection. Preoperative NLR and PLR were calculated from blood samples, with optimal cutoff values determined by receiver operating characteristic (ROC) analysis. Associations between NLR/PLR and clinicopathological features were evaluated, risk factors for LNM were analyzed via univariate and multivariate logistic regression.</p> Results <p>No significant differences were observed between the high NLR (H-NLR) and low NLR (L-NLR) groups in terms of clinicopathological characteristics, including TNM stage, perineural invasion (PNI), lymphovascular invasion (LVI), or serum levels of CEA and CA19-9 respectively (<i>p</i> &gt; 0.05).In contrast, the high PLR (H-PLR) group showed significantly higher prevalence of several adverse pathological features: The H-PLR group had a higher positive PNI (54.2% vs.25.0%,<i>p</i> = 0.04), greater positive LVI(51.6% vs.28.6%,<i>p</i> = 0.025),and more positive TDs (14.4% vs.0,<i>p</i> = 0.028), increased lymph node metastasis (52.9% vs.17.9%,<i>p</i> &lt; 0.001), more elevated CEA (43.1% vs.14.3%,<i>p</i> = 0.005) and more advanced tumor stage (stage II + stage III,81% vs.67.9%,<i>p</i> = 0.003).Univariate analysis identified several factors significantly associated with LNM: T stage (OR = 3.156, 95%CI:1.580–6.303),positive PNI (OR = 6.182,95%CI:3.242–11.787),positive LVI (OR = 10.271,95%CI:5.177–20.375),H-PLR(OR = 5.175,95%CI:1.870−14.321),positive TDs (OR = 3.390,95%CI:1.261–9.117),TLN(OR = 1.053,95%CI:1.005–1.103),elevated CEA(OR = 3.313,95%CI:1.655–5.920) and elevated CA199 (OR = 2.248,95%CI:1.012–4.992) were correlated with LNM using univariate analysis, but only positive LVI(adjusted OR = 6.203,95%CI:2.892–13.303,<i>p</i> &lt; 0.001) and positive PNI (adjusted OR = 3.086,95%CI:1.341–7.102,<i>p</i> = 0.008) were the independent risk factors for LNM using multivariate analysis.</p> Conclusion <p>H-PLR but not H-NLR may be associated with LNM, positive LVI and PNI were independent risk factors for LNM in RC.</p>