A fashion social platform is a system that leverages the power of social connectivity to enable individuals to interact, accumulate information and create social values in fashion marketing. Fashion social platform participants, through their collective intelligence, give social platforms essential competence to solve economic and social issues, gather social capital, and create customer value. This study highlights the critical value of fashion social platforms and explains the relationships between knowledge sharing, social capital, and sustainable customer value. They examine (1) the effects of social network properties on knowledge sharing in fashion social platforms, (2) the effects of knowledge sharing on social capital, and (3) the effects of social capital on customer value in fashion social platforms. In the context of social platforms, this study clarifies the concept of customer value, the role of knowledge sharing, and the relationships between social capital and customer value. The study constructs a theoretical model regarding fashion social platforms and sustainable customer value that offers possible implications for fashion marketing practitioners.