Objective: To illustrate the association between prolactin serum level and severity of preeclampsia. Methods: In this cross-sectional study, 31 pregnant women with preeclampsia were enrolled as GroupⅠand 20 healthy pregnant women as GroupⅡ. Routine investigations and prolactin serum levels were assessed together with blood pressure changes. The unpaired t-test was used to determine the differences and correlation coefficient for the evaluation of correlation. Results: Prolactin serum levels were higher in preeclampsia patients compared with those of the healthy pregnant women (P<0.001). The severity of preeclampsia was linked with prolactin serum levels since 20 patients with preeclampsia showed mild preeclampsia that illustrated relatively lower prolactin serum levels compared with 11 patients with severe preeclampsia (P<0.001). The severity of mean arterial blood pressure was significantly correlated with prolactin serum levels (r=0.78, P<0.001). Conclusions: Prolactin serum levels are elevated in patients with preeclampsia and correlated with the severity of preeclampsia. High but not normal prolactin might be implicated in the pathogenesis of preeclampsia.