Background: Preeclampsia is one of the commonest complications of pregnancy. Calcium deficiency is implicated in the development of preeclampsia especially in developing Countries. There is paucity of studies on the role of serum levels of calcium in preeclampsia in Southern Nigeria. Objective: The main objective of this study was to determine the serum level of calcium in women with preeclampsia and those without preeclampsia. Methodology: This was a comparative study in which 52 preeclamptic and 52 non preeclamptic women who satisfied the eligibility criteria were recruited for the study. Data entry and statistical analysis was done using statistical software (IBM SPSS® for windows version 21.0.) Data were analyzed for mean and standard deviation. Comparison of serum levels of calcium between the two groups was performed by student t-test and P value < 0.05 was considered as statistically significant. Results : The serum calcium level was statistically lower in women who had preeclampsia compared to those who did not (8.37±0.91 mg/dl vs 9.33±1.15mg/dl respectively, p<0.001).The systolic and diastolic blood pressure showed a significant negative correlation with serum calcium level in those that developed preeclampsia Conclusion : This study showed that women with preeclampsia demonstrated a significantly reduced serum calcium level. This support the hypothesis that hypocalcaemia is a possible aetiology of preeclampsia.