This paper studies the antecedents of active usage of mobile instant messaging (MIM) applications based on an attachment theory perspective. It proposes MIM identification; self-congruence, design aesthetics, interactivity, mobility and feedback can be the factors that influence active usage of MIM from a user-device attachment perspective. It also explores two working mechanisms of these factors: emotional attachment and functional dependence. By using a survey method, 294 valid responses were collected from Chinese active smartphone users and were analyzed using structural equation modelling. The results of the analysis indicate that MIM identification, self-congruence and design aesthetics influence emotional attachment significantly, and mobility and design aesthetics influence functional dependence significantly. Besides, interactivity and feedback do not have any significant impact on functional dependence. Implications for theory and practice are discussed.