Aim: The aim of this study was to investigate the effects of vitamin D treatment on ovary in experimentally designed polycystic ovary syndrome of female rats using light and electron microscopic techniques. Methods: Twenty-four female pre-pubertal rats were divided into control, DHEA and DHEA+Vit. D groups. In DHEA group, the PCOS rat model was developed by 6mg/kg/day dehydroepiandrosterone administration as subcutaneously injections. In DHEA+ Vit. D group, 6 mg/kg/day DHEA and 120ng/100g/week 1,25(OH) 2D3 was performed simultaneously. Controls were injected with vehicle alone. At the end of the 28 days, blood samples were collected and the ovarian tissues were taken for histological examinations. Results: FSH, LH levels, LH/FSH ratio, and testosterone levels showed a significant increase in DHEA group when compared with the control group. Moreover, these measurements were lower in the treatment group than the DHEA group. In DHEA group, increased number of atretic follicles and cystic follicles were seen with light microscopic analysis. Cystic follicles with attenuated granulosa cell layers and thickened theca cell layers and lipid accumulation in interstitial cells were observed by electron microscope. It is observed that atretic and cystic follicles were decreased as a result of vitamin D treatment. Conclusion: Our results indicate the curative role of vitamin D treatment on the androgen excess in PCOS rat model which causes abnormalities in ovarian morphology and functions. Vitamin D has positive effects on the hormonal and structural changes observed in PCOS, but it has been concluded that long-term use may be more beneficial.