Introduction: Predictive tests are needed to ensure the development and subsequent follow-up of pre-eclampsia, which is responsible for significant rates of morbidity and mortality during pregnancy. This study aimed to evaluate the predictive value of the Hemoglobin, Albumin, Lymphocyte, and Platelet (HALP) score for the severity of preeclampsia. Methods: We retrospectively analyzed the data of women diagnosed with pre-eclampsia at our clinic from January 2019 to January 2023. The control group consisted of normotensive, healthy pregnant women. Women diagnosed with preeclampsia were further evaluated in two groups: those with severe features and those without severe features. The clinical and demographic data of the cases were evaluated. The HALP score was calculated using the first trimester blood parameters of the cases and compared between groups. Results: The study included 229 patients with preeclampsia and 142 normotensive healthy controls. Of the patients with preeclampsia, 104 (28.1%) had severe features of the disease. The HALP score was significantly higher in the preeclampsia group with severe features than in the control group (6.18 ± 2.66 vs. 3.75 ± 1.86; p = 0.006). In multivariate logistic regression analysis, the HALP score (odds ratio: 2.02, 95% confidence interval: 1.10–3.32, p = 0.017) was found to be an independent indicator for preeclampsia with severe features. A HALP score of > 4.61 predicted the development of preeclampsia with severe features with a sensitivity of 74.5% and a specificity of 81.3%. Conclusion: We found a significant correlation between the HALP score and preeclampsia with severe features. The HALP score may be useful in predicting the severity of preeclampsia.