Brand switching refers to migration of users from one brand to another. Switching is associated with negative consequences such as declining market share and poor profitability. As such, mobile telecommunications user switching has become a critical issue facing mobile service providers. Drawn from an online self-completion survey of mobile telecommunications users (N = 24,141) across four countries, this study examines previously unexplored antecedent factors determining brand switching behavior of mobile telecommunications users, and the relative importance of those factors. The research identifies the overall dimensions of switching behavior and then validates a theoretical model. The regression model suggests weak coefficient of determination (R2) between the dependent and independent variables. The study bridges the theoretical and practical knowledge gap in the literature by examining factors influencing consumers' switching behavior. Two economically developed and two emerging economies were selected in this study to examine potential differences in consumers' behavior towards mobile telecommunications services in both emerging and developed markets, and help us understand the potential reasons for these differences.