Objective: Exposure to environmental toxicants such as copper has been suggested to have adverse effects on male reproduction. Therefore, our aim in the present study was to investigate morphometrical changes of rat testes following long term consumption. Methods: Animals were divided into three experimental groups. Two different doses of copper sulfate were applied once a day for 8 weeks by gavage. The first treatment group received copper sulfate at a dose of 100 mg/kg (Cu100 group) and the second treatment group was given copper sulfate at a dose of 200 mg/kg (Cu200 group). Control animals received normal saline using the same method. Testes from five cases of 15 animals of each group were removed for histopathological examinations on days 14, 28 and 56. Morphometrically, seminiferous tubules diameter, spermatogonial cells nuclei diameter, sertoli cells nuclei diameter and epithelial height were measured in the experimental groups. Meiotic index and the percentage of spermatogenesis were also calculated.Results: The mean values of about mentioned morphometrical parameters in copper treated groups showed significant decrease on 14th day compared to the control group. Copper administration caused a significant damage to morphometrical parameters on 28th day compared to the day 14. Also, in some parameters further decreases were observed specially in the Cu200 group on 56th day such as the diameter of seminiferous tubules, spermatogonial and sertoli cells nuclei and epithelial height of germinal layer (P<0.05). Conclusions: The results show that exposure to copper has the deleterious effects on morphometrical structure of testes which are appeared as early as two weeks.