Aim: The aim of this study was to investigate the use of serum soluble CD40 ligand (sCD40L) concentration values, measured between 11+0 and 13+6 weeks of pregnancy, in the prediction of preeclampsia development and to determine the presence of a statistically significant difference. Materials and Methods: sCD40L concentrations of 202 cases who were admitted to the present hospital for routine control between 11+0 and 13+6 gestational weeks were measured and antenatal follow up was performed until delivery. Results: Among 202 patients who completed gestational period, 172 subjects developed no preeclampsia, while two cases had severe and 28 cases had mild preeclampsia (30 subjects in total). sCD40L level was detected as 4212.35 ± 3366.46 pg/ml in normotensive pregnant cases, while it was 5244.63 ± 3633.27 pg/ml in the patients with preeclampsia. There was no statistically significant difference between preeclamptic and normotensive patient group in terms of sCD40L concentrations (p < 0.05). Conclusion: The authors revealed that the mean sCD40L did not significantly increase during first trimester in the patients with preeclampsia, while it showed a tendency to increase in these cases. They believe that other than sCD40L concentration values, consideration of other patient-related factors such as some parameters including S endoglin, and uterine artery pulsatility may provide more successful results in the prediction of preeclampsia. Therefore, prospective, randomized, and controlled studies are required to investigate the importance of sCD40L concentrations in the prediction of preeclampsia during first trimester.