Two experiments were carried out to study the effects of dietary supplementation with the garlic (Allium sativum)-derived product propyl propane thiosulfonate (PTS-O) on the intestinal log(10) number of copies of enteropathogens in broiler chickens, together with their intestinal morphology and growth performance. The additive had no significant effect on feed intake at any dose assayed. In experiment 1 (1 to 21 d of age), the BW of chickens fed on 45 mg of PTS-O/kg of diet was higher (P < 0.01) than that of controls. Birds fed on diets containing 45 and 90 mg of PTS-O/kg of diet had improved (P < 0.01) feed:gain ratios compared with the controls at 21 d of age. Ileal villus height, width and surface area, mucosal thickness, and muscular layer thickness were considerably greater (P < 0.01) than control values in chickens fed 90 mg of PTS-O/kg of diet. The Clostridium perfringens log(10) number of counts was not significantly affected at any dose assayed. The inclusion of PTS-O at both concentrations (45 and 90 mg/kg of diet) resulted in lower (P < 0.01) log(10) number of copies of ileal Salmonella spp. and crop enterobacteria and Escherichia coli. The inclusion of 90 mg of PTS-O/kg of diet also resulted in lower (P < 0.01) enterobacteria and E. coli log(10) numbers of copies in the ileal and cecal contents, respectively. The number of copies of Campylobacter jejuni was not significantly affected. In experiment 2 (15 to 28 d of age), lower (P < 0.01) log(10) number of copies of Salmonella spp. and C. jejuni were determined in the ileal contents of chickens fed on diets containing 135 mg of PTS-O/kg of diet. The addition of 90 mg of PTS-O/kg of diet lowered (P < 0.01) only the number of copies of ileal Salmonella spp. This investigation confirmed previous in vitro data and showed that PTS-O lowered the intestinal numbers of enteropathogens and improved the ileal histological structure and productive parameters of broilers.