As social commerce gains popularity, companies need to address service failure cases that cause expansive consumer damage. While existing literature has examined service failure in the traditional e-commerce market, the unique consumer relational characteristics of social commerce makes it difficult to directly extend current understanding to this business model. Founded on the attribution-affect-behaviour model, this study examines consumer-perceived source of service failure and its impact on negative emotions and post-purchase behaviours. A survey of 300 active social commerce users who have experienced at least one service failure shows that consumers blame failed incidents on social commerce companies and merchants. Regret and disappointment lead to dissatisfaction. Dissatisfied consumers spread negative e-WOM and have lower tendency to repurchase from the same social commerce sites. This study underscores the importance of close collaboration between social commerce companies and merchants in delivering satisfactory services to customers.