Six hundred day old unsexed broiler chicks were used in a 42-d trial at Chittagong Veterinary and Animal Science University Poultry Farm to compare the effects of different levels of fish oil supplementation on performance of broilers in terms of feed intake, weight gain and feed conversion and carcass characteristics. The chicks were randomly distributed following a completely randomized design in four groups having three replications per group. Each group was composed of 150 chicks and 50 birds per replicate. Four diets were formulated using locally available ingredients as diet without oil, diets containing 2.5%, 3.0% and 3.5% fish oil. Results indicated that, supplementation of diets with different levels of fish oil significantly differed (P<0.05) feed intake at 1st, 3rd, 4th and 6th weeks of age. However, there was no significant (P>0.05) effect of fish oil supplementation on feed conversion up to 5th week of age. At the end of 6th week, feed conversion of the broilers of different dietary groups differed significantly (P<0.05). Similarly, no significant differences (P>0.05) were found among all dietary treatment groups in weight gain up to 3rd week of age except at later stages. Out of eighteen parameters, shank weight, heart weight, thigh bone weight and abdominal fat weight differed (P<0.05) due to supplementation of fish oil. It can be concluded that, supplementation of fish oil at 2.5% level results in the best cumulative feed intake and feed conversion of broilers.