To assess the early predictive value of maternal parameters for early-onset sepsis (EOS) in preterm infants, especially including the maternal neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and mean platelet volume (MPV). The retrospective cohort study examined a total of 231 preterm infants (69 with EOS) from May 2017 to October 2021 of the Fourth Hospital of Hebei Medical University, randomly divided (7:3) into the training set group (n = 162) and validation set group (n = 69). Thirteen clinical variables (including MPV, NLR, and PLR) were included as the research objects. By logistic regression, the factors significantly associated with EOS were distinguished. Additionally, a nomogram was constructed based on the independent risk factors, the validation of which relied on the concordance index, calibration curves, receiver operating characteristic curves, and decision curve analyses. Multivariate logistic regression proved that NLR (OR = 1.67, 95% CI = 1.18-2.36, P = .004), PLR (OR = 1.03, 95% CI = 1.01-1.04, P = .001), and MPV (OR = 1.75, 95% CI = 1.15-2.66, P = .009) were independent risk factors for EOS. The AUC of the nomogram for the training set group was 0.872 (0.814, 0.931) and 0.889 (0.843, 0.935) in the validation set group. The P values of Hosmer-Lemeshow test for the training set and validation set groups were .903 and .752, respectively. The decision curve analyses outcome indicated good clinical practicability. The C-index for the training set and validation set groups were 0.872 and 0.889, respectively. The maternal NLR, PLR, and MPV levels had good predictive value for EOS in premature infants. The nomogram in our study could help clinicians predict the occurrence of EOS.