To investigate the effect of two dietary levels of l-carnitine and vegetable fat powder on the quality of cockerels' sperm and broiler breeder fertility and hatchability. Two hundred and fifty female and twenty five male broiler breeders. were studied Classic Hubbard parent stocks were randomly distributed in five groups of 50 with five replicates of 10 females and one male. Two levels of l-carnitine 0, 60 ppm(for females) and 0, 500 ppm (for males) and vegetable fat powder(0, 1. 5%) were used in a completely random design. At first, data were analyzed in factorial arrangement but no interaction was observed and then a completely randomized design was employed. A diet with high lysine and methionine was fed to one group of birds. Determined variables were hatchability, fertility, egg production, egg weight, albumen height, Hugh unit, color of yolk, shell thickness, shell strength, semen volume, sperm motility, live sperm percent, sperm count and normal sperm percent. Supplemented diet with l-carnitine had significant effects during the hatchability (p<0. 01-0. 05), fertility (p<0. 01), semen quantity and sperm quality (p<0. 01). L-carnitine had no effect on egg production except on fifth and sixth weeks of experiment (p<0. 01); also, l-carnitine had no effect on egg characteristics. Supplementation of l-carnitine in broiler breeders rations increases their fertility, hatchability and sperm quality.