Abstract : Polycystic ovary syndrome (PCOS) is a common abnormality among young women in their reproductive age. It is associated with complications such as insulin resistance, lipid profile and metabolic disorders. This study compared the relationship between vitamin D level and complications of obesity, dyslipidemia and insulin resistance in women with and without PCOS. One hundred and forty women were evaluated in this cross-sectional study (70 in PCOS and 70 in control groups). 5 cc of blood was taken from all participants to evaluate their fasting blood glucose, lipid profiles, and insulin levels. The rate of insulin resistance was calculated with the homeostatic model of insulin resistance (HOMA-IR) formula. Analysis of variance and T-test were used to compare the quantitative data with a normal distribution. Non-parametric tests were used to compare data with a non-normal distribution. The association of the level of vitamin D and metabolic variables was studied with Pearson’s and Spearman’s coefficients. The vitamin D3 levels were significantly lower in PCOS group compared to the control group. However, the body mass index, insulin resistance, fasting insulin and low-density lipoprotein (LDL) cholesterol levels were significantly higher in the PCOS group (P < 0.05). Based on Pearson’s correlation coefficient, within the PCOS group a significant, negative linear relationship among vitamin D3 level and body mass index is existing (P < 0.05). In women with a hormonal disorder of PCOS, vitamin D3 could have a critical role in the pathogenesis of insulin resistance