A factorial experiment was conducted to investigate the effects of L-Carnitine and fenofibrate on broilers. There were four replicates of four treatments, with each replicate including ten male Ross 308 broiler chickens. The experiment was conducted over a 42-day period. The treatments consisted of two levels of L-Carnitine (200 and 400 mg/kg) and two levels of fenofibrate (50 and 100 mg/kg) as supplements to a basal diet. Growth, carcass characteristics, serum constituents, immune system responsiveness, cecal microflora, sensory attributes and fatty acid profiles of breast meat, and small intestine histology were characterized. During the finishing period, the chickens fed a diet containing 400 mg/kg L-Carnitine and 50 or 100 mg/kg fenofibrate had lower feed intake andfeed conversion ratio (FCR) and higher weight than the other treatments. Application of 400 mg/kg L-Carnitine in combination with two levels of fenofibrate reduced ventricular fat (P <0.05), cholesterol (P <0.01), triglycerides (P <0.05), and very low density lipoprotein (VLDL) (P <0.05). These treatments increased antibody titers against Newcastle disease (ND)and avian influenza virus (AIV). Among the sensory properties of breast meat, experimental treatments had a significant effect only on its aroma (P <0.05). In general, supplementing the diet of Ross 308 broilers with 400 mg/kg L-Carnitine and 50 or 100 mg/kg of fenofibrate is recommended.