As consumers have transformed into the influential entities in the recent consumption environment, it needs a new concept to describe their characteristics. Drawn on the notion of smart consumer experience, this study views the multiple traits of new consumers as consumer smartness. Therefore, elaborating the concept of consumer smartness, this study aims to develop its measurement and validate it by examining the relationship with external variables. Two online surveys were conducted by a professional survey company that had nationwide consumer panels. A total of 531 adult consumers who had purchased fashion goods online completed a self-administered questionnaires. A series of exploratory and confirmative factor analysis generated 21 measuring items with six underlying constructs of consumer smartness such as innovativeness, opinion leadership, self-disclosure, marketing literacy, dissatisfaction, and technology sophistication. In order to validate the measurement, this study conducted a Pearson’s correlation test and structural equation modeling analysis with consumer smartness and external constructs. The result shows that there was a significant positive relationship between consumer smartness and behavioral intentions online. In addition, consumer smartness influenced their shopping and sharing intention which supported the validity of new measurement of consumer smartness. This study provides a theoretical and empirical ground of understanding consumer smartness as new consumer characteristics in the changing environment of fashion retailing.