Consumers are empowered to exert influence on brands through social networking sites (SNSs), which make it possible for consumers to become active content creators in their relationship with firms. To further understand brand value co-creation, we use the socio-technical theory to build a model of brand co-creation with key antecedents−social commerce information sharing, social support, and relationship quality, with privacy concerns as a moderator. Through an empirical study, we found that social commerce information sharing, social support and relationship quality positively affect brand co-creation directly/indirectly and privacy concerns moderate the effects of social commerce information sharing on brand co-creation. This article contributes to the literature on the value co-creation paradigm and social commerce by: 1) developing the concept of brand co-creation in social commerce; 2) explaining how consumers engage in online brand co-creation activities; 3) arguing that privacy concerns may hamper the effects of brand co-creation. Our study provides an innovative approach to brand management practices in today's marketplace.