A cross sectional study was conducted in the Department of Biochemistry, Dhaka Medical College, Dhaka, from July 2017 to June 2018 to evaluate the serum calcium level in umbilical cord of preterm and term babies. In this study, hundred newborn babies were selected according to selection criteria from the Department of Obstetrics, Dhaka Medical College Hospital, Dhaka. Among them fifty were preterm (Group A) and fifty were term babies (Group B). Informed written consent from the mother or legal guardian of babies was taken after full explanation of procedure regarding this study. In Group A, mean+/-SD of serum calcium was 7.28+/-0.69 (mg/dl) where as in Group B, mean+/-SD of serum calcium was 9.42+/-0.70 (mg/dl). This value was significantly lower (p<0.001) in Group A than Group B. Serum calcium has significant (p<0.001) positive correlation with gestational age but no significant correlation with birth weight. Finding of this study might be helpful for early diagnosis of calcium deficiency in the preterm babies and also help to prevent the deficiency related neonatal morbidity and mortality.