This study aimed to compare the first trimester complete blood count (CBC) indices of pregnancies complicated by early-onset preeclampsia (EOPE) or late-onset preeclampsia (LOPE). A retrospective case-control study was conducted with 186 patients. Patients were classified into three subgroups: EOPE, LOPE, and control groups. First trimester CBC results were obtained for each patient. Hemoglobin, hematocrit, red blood cell distribution width, mean corpuscular volume, white blood cell (WBC) count, neutrophil, eosinophil, basophil, lymphocyte, monocyte, mean platelet volume, platelet distribution width, plateletcrit, and platelet count were compared. The neutrophil lymphocyte ratio was calculated by dividing the absolute lymphocyte count by the absolute neutrophil count. The platelet lymphocyte ratio was calculated by dividing the absolute lymphocyte count by the absolute platelet count. The total number of cases was 21, 42, and 123, in the EOPE, LOPE, and control groups, respectively. There were statistically significant differences in the total WBC and neutrophil counts between the three groups (both p<0.05). WBC and neutrophil counts were found to be highest in the EOPE group, and the LOPE group had higher levels compared with controls. The optimal cut-off values to predict EOPE for WBC and neutrophil counts were 9.55×103/ μL (sensitivity 71.4% and specificity 70.7%) and 6.45×103/μL (sensitivity 66.7% and specificity 74.8%), respectively. Increased first trimester WBC and neutrophil counts may be predictive for EOPE.