Free radicals increase in the presence of diabetes. Lycopene is a powerful antioxidant. The goal of the present study was to determine the effect of diabetes on rat ovaries and the protective role of lycopene in that context. Experimental diabetes was induced with 50 mg÷kg streptozotocin. Rats were randomly separated into four groups， as follows: control + corn oil， control + lycopene， diabetes + corn oil and diabetes + lycopene. The histological and histometric evaluations were performed using Crossman's triple staining method. The immunohistochemical connexin-43 expression was identified and the apoptotic cell density was determined using the terminal deoxynucleotidyl transferase dUTP nick-end labeling method， while the malondialdehyde levels were measured using the enzyme-linked immunosorbent assay technique in the ovaries. Vacuolization of the corpus luteum， hydropic degeneration in the interstitial regions， and the number of corpora lutea increased in the ovary as effects of diabetes while the diameter of the corpora lutea decreased. The intensity of connexin-43 expression decreased in the primordial and atretic follicles， interstitial cells and luteal cells of the corpora lutea in the diabetes + corn oil group. The ovarian malondialdehyde levels and the number of apoptotic cells in the granulose layers of the large antral follicles increased in the presence of diabetes. Lycopene increased the expression of connexin-43 in the primordial， secondary and large antral follicles in the ovaries of diabetic animals. The changes caused by diabetes in the ovaries and the protective role of lycopene in some but not all parameters was revealed.