Abstract: In order to assess the effect of a probiotic and population density on the growth performance and the carcass characteristics in broiler chickens, an experiment was conducted involving 208 1-day-old Peterson brand chicks. They were fed a corn and soy paste diet with 23 and 20 percent crude protein at the first and last stage respectively and 3.2 Mcal ME/kg. A completely randomized design with a 2 x 2 factorial arrangement, with two probiotics levels: 0 y 0.1% and two population density levels: 10 and 16 birds/m2, with four repetitions per treatment. The evaluation centered on growth performance: weight gain, feed consumption, food conversion and carcass variables: hot and chilled carcass weight, as well as breast, leg and thigh output. The growth performance was not affected (P>0.05) by probiotic and population density. The greatest yields (P<0.05) in the hot carcass weight was reported from the interaction between 0.1% probiotic and 10 birds/m2. The probiotic increased (P<0.05) the lean leg meat. The density of 16 birds/m2 showed the highest yield (P<0.05) in leg fat versus 10 birds/m2. The results of this study indicated that, 0.1% probiotic increased the lean leg meat yield and the population density of 16 birds/m2 generates a higher fat deposit in broiler chickens.