In this study, the effect of Nigella Sativa on the formation of obesity was investigated histopathologically and biochemically in rats fed with high fat diet and gained weight gain. For this aim, thirty-two (32) rats were randomly separated in four groups, to be eighth (8) rats in each group, control (n=8), obesity (n=8), Obesity +Nigella sativa (n=8) and Nigella sativa (n=8). The Control group was fed with standard rat pellet feed. The Obesity Group was fed pellet feed with a high energy value diet. The Obesity+Nigella sativa extract group was fed with high energy value diet pellet feed, additionally, Nigella sativa extract was daily given the dose of 3mg/kg/rat with an orogastric gavage. The Nigella sativa extract group was fed with standard pellet feed, additionally, Nigella sativa extract was daily given the dose of 3 mg/kg/rat with an orogastric gavage. During the experiment, the weight gaining of rats was tracked. At the end of the experiment, blood and tissue samples were taken from the necropsied rats for biochemical and histopathological examinations. In blood serum samples; Alanine transaminase (ALT), aspartic transaminase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), gamma glutamyl transferase (GGT), cholesterol, triglyceride, HDL cholesterol, LDL cholesterol and fasting blood glucose (FBG) activities were determined. Histopathologically, in the Obesity group, sharply circumscribed fat vacuoles of different sizes in centrilobuler hepatocytes in the liver and coagulation necrosis in some of the hepatocytes were observed, while in the Obesity + Nigella Sativa group and Nigella Sativa group the liver was observed normal histological appearance like in the control group. Biochemically, triglyceride level in obesity group; It was observed that it was significantly higher than the control, Obesity + Nigella Sativa and Nigella Sativa groups. In the Obesity + Nigella Sativa group; Serum ALT level was significantly higher than the control and obesity groups, while ALP, HDL, triglyceride and FPG activities increased significantly compared to the control group. The Nigella sativa extract group was quite similar to that of the control group. As a result, In addition to high fat diet, Nigella Sativa extract greatly prevented fatty liver changes in rats. This research was supported by the Scientific Research Projects Directorate of Van Yüzüncü Yıl University as a project numbered TYL-2019-8290 (ID: 8290).