Chlorine dioxide (ClO2) is a powerful biocide that has long been used commercially to control microbial activity in various sectors. This study was conducted to determine the effectiveness of dietary ClO2 on growth performance, intestinal and excreta microorganisms, and the emission of odorous gas from broiler excreta. A total of 120 one-day-old broiler chicks were provided with experimental diets including ClO2 at 0, 0.05, or 0.1% of the diet at random. Dietary ClO2 (0.05 and 0.1%) resulted in a significant reduction in feed intake and feed conversion ratio without affecting the growth rate of the broilers. Dietary ClO2 (0.05 and 0.1%) did not affect the Lactobacillus, Bacillus, and Salmonella concentrations in the ileal digesta; however, it significantly increased the level of yeast and mold. In contrast, dietary ClO2 at 0.1% significantly decreased the number of ileal E. coli. In the cecal digesta, the Bacillus, E. coli and Salmonella CFUs were reduced significantly in response to 0.05 and 0.1% ClO2. Both levels of ClO2 significantly reduced the concentrations of E. coli and Salmonella in broiler excreta by d 21, whereas significant reduction was observed only in response to 0.1% ClO2 supplementation by d 35. Dietary supplementation with 0.1% ClO2 resulted in significant reductions in excreta pH at 6, 12, and 48 h of incubation relative to the non-supplemented group. Fecal ammonia emission was significantly higher at 48 h in response to 0.1% ClO2 supplementation. In contrast, significantly lower emissions of hydrogen sulfide (3, 6, 12, and 24 h), sulfur dioxide (24 and 48 h), and mercaptans (0, 3, and 48 h) were recorded in response to dietary ClO2 supplementation. Overall, reduction of intestinal and excreta pathogenic microorganisms together with lower emissions of sulfur-containing odorous gas from broiler excreta were observed in response to dietary supplementation with 0.1% ClO2 without affecting the growth rate.