The aim of this study was to investigate the effect of water activity (aw) on inactivation of Listeria monocytogenes using gaseous chlorine dioxide (ClO2 (g)) under room temperature. Surface-inoculated tryptic soy agar (TSA) plates adjusted to 9 different water activity levels ranging from 0.994 to 0.429 were used as samples exposed to ClO2 (g) at 150, 250, and 350 ppm for different durations of treatment time. Results showed that the antimicrobial effect of ClO2 (g) significantly decreases as the aw level and ClO2 (g) concentration decrease. Nonlinear models, such as the modified Chick model and the Weibull model, were used to describe the inactivation kinetics of L. monocytogenes. The results showed that the modified Chick model, which is based on chemical reaction kinetics, was more suitable to describe the inactivation of L. monocytogenes (RMSE < 0.5 log CFU/g) than the Weibull model (RMSE < 1.0 log CFU/g). A multiple regression model was developed for the describing the effect of aw and ClO2 (g) concentration on bacterial inactivation. The results of this study may be used to design ClO2 (g) treatment processes to inactivate L. monocytogenes in low-moisture foods. Published by Elsevier Ltd.