OBJECTIVE: To evaluate the efficacy of calcium & vitamin D supplementation in infertile women suffering from polycystic ovary syndrome (PCOS), and to assess levels of 25-hydroxy vitamin D in these patients. METHODS: In a case control study, 100 infertile PCOS women based on a randomly divided into two groups. Group I (n = 50) were treated with metformin 1500 mg/day, and group II (n = 50) treated with metformin 1500 mg/day plus Calcium 1000 mg/day and Vitamin D 100000 IU/month for 6 months. Patients were followed by transvaginal sonography at first, 3 and 6 months later for evaluating dominant follicle. BMI, menstrual regularity, follicle diameter, pregnancy, serum 25-OH-vitamin D level were matured and compared in two groups. RESULTS: BMI decreased almost significantly (25.49 ± 1.88 vs 26.28 ± 2.15, p: 0.054) in group II. A better improvement was gained in regulating menstrual abnormalities (70% vs 58%, p: 0.211), follicle maturation (28% vs 22%, p: 0.698), and infertility (18% vs 12%, p: 0.401) in group II compared with group I, but these results were not statistically significant. Eighty three percent of all the PCOS patients showed vitamin D deficiency while 35% were severely deficient. The serum 25-OH-vitamin D mean levels were 13.38 ± 6.48 ng/ml. Vitamin D deficiency was recompensed in 74% of the PCOS patients who had taken calcium & vitamin D supplementation. There was no correlation between BMI and 25-OH-VD before and after the treatment (p ≥ 0.01). CONCLUSION: This study showed the positive effects of calcium & vitamin D supplementation on weight loss, follicle maturation, menstrual regularity, and improvement of hyperandrogenism, in infertile women with PCOS.