The aim of the study was to evaluate the standardized allicin effect on the health, productivity and meat quality of broilers. The antimicrobial properties of the preparation and its impact on the intestinal microbiota were evaluated. It was also attempted to determine the lowest effective dose of preparation. 960 Ross 308 chickens were divided into 4 groups (8 replications each). Birds were maintained in a litter pen with a stocking density of 33 kg/m2 and constant access to feed and water. The groups were differentiated by the preparation used: group 1 (control), without supplementation, then standardized allicin doses of 150, 200 and 250 μg/kg body weight were applied in group 2, 3 and 4, respectively at 3-day intervals. The birds’ productivity was recorded over 42 days, then 16 birds/ group were slaughtered and dissected. Samples of meat were collected. There were no differences in the final body weight of the birds, but significantly the lowest feed conversion ratio and highest livability rate in group 4 were found. The allicin-supplemented groups showed a lower incidence of foot pad dermatitis, as well as a quantitative reduction in the aerobic bacteria in the intestinal contents. No effect on the quality of the meat obtained was noticed.