Smoking is a considerable problem in modern populations. Nicotine, as an important noxious material in cigarette, has dangerous effects on different body tissues such as genital system. In this study the noxious effect of nicotine was investigated in rat ovarian follicles by histomorphometry technique. Three groups of mature female rats including control, low-dose nicotine [0.2mg/kg. BW] , and high-dose nicotine [0.4mg/kg. BW] were planned. Nicotine was injected through intraperitoneal route for 21 consecutive days. Then, the rats were euthanized by carbon dioxide and immediately their ovaries were removed and fixed in formal saline solution. The specimens were processed through routine paraffin embedding method, serially sectioned by microtome, stained with hematoxylin-Eosin technique and investigated by light microscope. The data were analyzed using one-way ANOVA and Tukey’s multiple comparison tests. p<0.05 was considered statistically significant. The results of this study demonstrated that distribution of ovarian follicles in animals receiving either low or high doses of nicotine decreased significantly, whereas distribution of atretic follicles notably increased as compared with the control group. Based on the results of this study, on a dose-related pattern, nicotine could decrease the population of the healthy ovarian follicles, whereas increased the population of the atretic ovarian follicles. This indicates reduction of fertility in affected animals