Di-(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer and people are exposed to various amounts on a daily basis. This study was designed to evaluate the genotoxic, histologic, immunohistochemical, morphometric and hormonal effects of DEHP (100, 200 and 400 mg kg(-1) per day DEHP) administered daily to rats by oral gavage for 28 days. The rats were divided into five groups including oil control, positive control (MMS) and treatment groups (100, 200 and 400 mg kg(-1) per day DEHP). They were euthanized at the end of the experiment, organ and body weights were recorded and serum was collected for biochemical and hormone analysis. The genotoxic effect was measured in blood and sperm using the Comet assay. The testes, epididymis, prostate gland and seminal vesicle were collected and stained with hematoxylin and eosin for histopathologic analysis. Epithelial height, luminal and tubular diameters (M) in seminiferous tubules were also measured. Moreover, the study revealed an increase in the DNA damage level in both blood lymphocytes and sperm. At the end of the experiment, the tail intensity showed a significant increase in the 100 mg kg(-1) per day (p = 0.032), 200 mg kg(-1) per day (p = 0.019) and 400 mg kg(-1) per day (p = 0.012) dose groups compared to the control group in blood. Furthermore, testosterone was decreased in all treatment groups compared to the control group. Besides, DEHP caused a significant decrease in the leukocyte levels (p = 0.017) and hemoglobin content, as well as an increased mean cell volume (MCV) count (p = 0.029) in the 400 mg kg(-1) per day group when compared to the control values. It is important to indicate that there were apoptotic cells seen in the lumen of testes in the 200 and 400 mg kg(-1) per day dose groups using the Tunel method. Therefore, with this study, it has been illustrated that DEHP caused DNA damage in blood and sperm and concrete negative effects on the reproductive system in rats from the pre-pubertal period to the pubertal period. This is a unique study since there has not been any other study that presents the indicated level of DNA damage while considering the genotoxic, histologic, immunohistochemical, morphometric and hormonal effects of DEHP.