We evaluated microbial inactivation in chicken cage litter, to ensure microbial safety, using aqueous chloride dioxide. Contamination by coliforms, Escherichia coli, Listeria spp., yeasts and molds, total aerobic bacteria, and Salmonella spp. was detected in fresh cage litter, and microbial populations increased if litters were repeatedly used. Aqueous $ClO_2$ treatment (500 ppm) significantly decreased the populations of coliforms, E. coli, Listeria spp., yeasts and molds, total aerobic bacteria, and Salmonella spp. in all litter samples tested. In particular, aqueous $ClO_2$ treatment on fresh litter reduced the initial populations of coliform, E. coli, Listeria spp., yeasts and molds, and total aerobic bacteria by 4.47, 1.29, 1.23, 3.24, and 5.2 log CFU/g, respectively. In addition, when litters used for 1 and 5 weeks were tested, treatment significantly reduced microbial populations. The results suggest that aqueous $ClO_2$ treatment is useful to reduce microbial hazards in chicken cage litter and to improve the microbial safety of slaughtered chickens.