ABSTRACT This study was designed to determine the effect of a combination of propionic-acetic acid on body weight, the relative weight of some organs, lactic acid bacteria, and intestinal pH of neonatal broilers. A total of 60 1-day-old Ross 308® broiler chickens were randomly placed in metabolic cages to two treatments, three replicates, and ten birds per replicates. The treatments consisted of a control diet (CD) and CD + 0.03% of propionic acid and acetic acid in the drinking water at a rate of 4 ml/L of water. The combination of organic acids depressed the body weight in neonatal broilers (p<0.05) and increased the relative weight (p<0.05) of gizzard, proventriculus, small intestine, and liver; also acidified the cecum with a significant decrease (p<0.05) of the pH. Also, these organic acids increased (p<0.05) the count of green bacilli with a white halo in the small intestine and decreased (p<0.05) the proliferation of irregular flat green bacilli in the cecum, although for both intestinal portions, the total lactic acid bacteria count was not different (p>0.05) between treatments. The combined use in the diet and drinking water of the propionic and acetic organic acids, respectively, reduced the bodyweight of neonatal broilers (10 days) and the cecal pH, as well as modified the relative weights of some digestive organs and the growth of some morphological groups of lactic acid bacteria.