Abstract. The aim of this study is to investigate the histopathological effects on the liver tissues of widely used as plasticizer Diisobutyl phthalate (DIBP). In this study Wistar albino (n=10) rats were used. Three study groups were created: an experimental group, a control group fed with corn oil and a control group. The experimental group were administered by gavaj daily with 3 different dosages (0.25 - 0.5 - 1 ml/kg/day) of DIBP mixed with corn oil for 28 days. The liver tissue sections after rutin histological preparation processes were examined and photographed using an Olympus BX51 light microscope. It was determined from the analyses that there was no significant histological difference between the control and the corn-oil fed control group. The group which was administered DIBP displayed deterioration in lobulation, focal hepatocellular necrosis, oedema in hepatic artery and vena centralis, decrease in glycogen and distortion of nucleus shape in relation to the dosage of DIBP they received. As a result, it has been determined that DIBP is a hepatotoxic substance and has been found to cause irreversible serious histopathological changes in liver tissue.Keywords: Diisobutyl phthalate, liver, histopatology, rat