An experiment was conducted in order to study the effect of 3 levels of fat (1, 3, 5%) and 2 levels of L-camitine (0 and 250 mg kg(-1)) on 360 male Ross broiler chicks in a factorial arrangement (2 x 3) with completely randomized design with 6 treatments, 4 replicates and 15 chicks in each replicates. All diets were isocaloric and isonitrogenous and were fed to chicks from 1 to 42 days of ages. During the experiment feed intake, body weight gain and feed conversion ratio were measured weekly. Mortality was measured throughout the experiment. At 42 days of ages 4 birds from each treatment were slaughtered for determination of carcass characteristics and serum composition. Data of the experiment were analyzed by GLM procedure of SAS. Increasing of fat in the diets significantly improved performance of chicks in grower (22 to 42 days) and whole period (1 to 42 days) of the experiment (p < 0.05). Chicks fed with diets containing 3% fat had the highest breast meat and lowest abdominal fat percentage (p < 0.05). Adding L-carnitine to diets had not significant effect on performance and carcass characteristics. Interaction between fat and L-carnitine was significant on liver weight (p < 0.05). The levels of triglyceride (TG) and glucose in blood serum were affected by increasing of dietary fat (p < 0.05). Adding L-carnitine to diets significantly decreased the level of serum triglyceride, cholesterol and VLDL (p < 0.05). Dietary treatments had not significant effect on mortality.