Objective: To evaluate the immunomodulatory role of vitamin D3 in prevention of pregnancy loss in cases of recurrent miscarriage. Patients and methods: A total of 40 pregnant women with gestational age at or less than 6 weeks with recurrent miscarriage were enrolled in the present study and randomly assigned to study and control group each (n = 20 for each group) after fulfilling certain inclusion and exclusion criteria. All participants were assessed through complete history, general and obstetric history, ultrasound assessment and routine full laboratory evaluation. IFN-γ was assessed at ⩽6 week gestation on recruitment, then after treatment every 2 weeks till 14th week for both groups. Both groups received standard measures for cases with recurrent miscarriage. Study group participants were treated with oral vitamin D3 supplementation. Outcome measures included continuing pregnancy rate and change in INF-γ values between first and final assays. Results: No statistically significant difference was noted between both groups regarding baseline demographic, clinical characteristics and ultrasonographic findings. Control group participants were found to have significantly higher levels of IFN-γ compared to the study group after treatment. Risk of miscarriage was 15% lower among the study group than the control group. Continuing pregnancy rate was 70% in the study group and 55% in the control group. No significant difference was found between both groups regarding symptoms suggesting vitamin D3 side effects. Conclusion: Although statistically insignificant, vitamin D3 oral supplementation has resulted in reducing risk of pregnancy loss up to 15% among women with recurrent miscarriage so it is a matter that is worth more attention and large scale studies with larger sample size may result in more significant results.