This study investigated the effects of replacement of fish oil with dietary sesame oil (SO) on growth performance and fillet composition of rainbow trout ( Oncorhynchus mykiss) juvenile with initial mean body weight 52.54 ± 2.03 . Triplicate groups of 30 fish each held under identical culture conditions were fed twice daily by iso-nitrogenous, iso-calorific and iso-lipidic diets for 8 weeks. Experimental diets consisted of 36.96% protein and 18.52% lipid from fish oil (T1) 75% fish oil with 25% sesame oil(T2), 50% fish oil with 50% sesame oil (T3),  25% fish oil with 75% sesame oil (T4) ) and sesame oil (T5). Dietary sesame oil had no significant effect on growth rate or feed conversion ratio but the group was fed 100 % sesame oil had lower final body weight compare with others. SGR had been effect by oil source in diet and this index was decreased by increasing of sesame oil in diets. The VSI and HSI were changed by changing of diets and VSI was significantly higher in fish fed sesame oil only. The condition factor of fish reared on T5 was significantly higher than other groups. These treatments were affected on body composition, The carcass lipid content was lower in fish fed sesame oil. In contrast, protein content in carcass was higher in fish fed sesame oil. no significant differences were observed between dietary treatments for ash content in carcass of rainbow trout. The present results indicate that rainbow trout juvenile can be reared on diets in which FO has been replaced with SO, with no significant effects on fish performance.