Background: In recent years, dietary fat supplementation has become a common practice and fat supplemented diets have had variable effects on animal performance and carcass characteristics. OBJECTIVES: This study was conducted to determine the effect of  increasing the levels of sesame oil on performance, rumen parameters and plasma lipid profile in finishing Chal lambs. METHODS: Eighteen male lambs were fed with control (C; without sesame oil) and the diets contained low level (LSO; 2.5%) and high level (HSO; 5%) of sesame oil. RESULTS: The addition of fat had no effect on dry matter intake (DMI), average daily gain (ADG), feed conversion ratio (FCR) and carcass weight. Treatments with sesame oil had no effect on rumen ammonia concentration and total protozoal count. Ruminal pH was numerically smaller (p=0.14) for control compared to lambs fed diets containing 2.5 and 5% sesame oil. Treatments had no effect on total VFA, acetate, butyrate, valerate and isovalerate concentrations. The propionate concentration decreased (p=0.04) by supplementation of sesame oil compared with the control. Total cholesterol (TC) and HDL increased and the tendency for VLDL and triglyceride (p=0.13) to increase was observed by treatment groups when compared with the control. Glucose concentration and LDL were not affected by treatment. CONCLUSIONS: Sesame oil had no effect on the performance and carcass weight of lambs but there was decrease in blood cholesterol concentration.