Psychological ownership (PO), a feeling of possessiveness and psychological attachment of an object, is ubiquitous. Previous studies have demonstrated the importance of PO on individuals’ attitude and behaviors in organizations. However, few studies have empirically tested this concept in the online context, especially in social media. Basing on examining the antecedents and consequences of PO, this study aims to explore the effect of PO on customer engagement process and loyalty in online social media context. The proposed model was empirically evaluated using data via questionnaire survey in Taiwan. More than 350 LINE users participated in this study. Structural equation modelling was applied to analyze the results. We find that self-investment, perceived control, perceived familiarity and social influence have positive and significant effects on PO, which further influence online social media users’ loyalty. Moreover, this study generates new finding to PO literature by proposing social influence as a critical driver. Finally, the implications of this study on theory and practice are discussed.