This study examines that users’ usage need fulfillment and interactivity are determinants of platform trust in the context of WeChat which is the most popular social networking service based on smart phones in China. As social network services (SNSs) are turning to a commerce tool from a communication tool, this study also examines that the role of platform trust is a determinant of purchase intention. Moreover, this study identifies antecedents of the usage need fulfillment such as eWOM and interactivity dimensions and verifies their effects on platform trust in the WeChat-based social commerce setting. To test the proposed hypotheses, this study conducted an AMOS 20.0 analysis with a total of 482 data items collected from WeChat users in China. The key findings are as follows: First, instrumental and social need fulfillment in the usage need fulfillment dimension positively influence platform trust. Second, responsiveness control, two-way communication and ubiquitous connectivity in interactivity dimension positively influence platform trust. Third, platform trust is a determinant of purchase intention.