Abstract Background: Emerging data identifies critical roles for vitamin D and many areas of medicine are involved: regulation of cellular growth, immunity, central nervous system, cardiovascular diseases, and reproduction. Objective: To determine the impact of serum vitamin D level on ICSI cycle outcome. Design: A prospective cohort study. Methods: Patients who will undergo ICSI cycle with age ≤ 38 years , adequate ovarian reserve were included in this study., women with poor ovarian reserve and patients with freeze all cycles were excluded. Vitamin D Serum samples were obtained On the day of the ovum pick-up, participants were divided into 2 groups :Deficiency: (serum vitamin D ≤30ng/ml), Sufficiency: (serum vitamin D≥30ng/ml ).Quantitative B-hCG was done 14 days after emberyo transfer Result : A total of 135 women were included in the study after undergoing ICSI , women were divided into two groups as following :Group A:(n = 68) with serum vitamin D level ≥30 ng/ml and Group B:(n = 67) with serum vitamin D level < 30 ng/ml at day of ovum pick-up.. pregnancy was significantly higher in group A (76.5 %) compared to group B (58.2 %) with P-value < 0.05. With regards to pregnancy continuation there was significant increase in ongoing pregnancy among group A (88.5 %) compared to group B (61.5 %) and significant decrease in the number of aborted cases among group A (11.5 %) compared to group B (38.5 %) with P-value < 0.05. Conclusions: Vitamin D serum level may play a role in ICSI cycle out come . and it seems to valuable to adjust its level in patients with deficiency before starting their ICSI cycle