This study explores the multidimensional construct of brand authenticity and the effect of each component on brand attachment, brand commitment, and brand loyalty by focusing on fashion brands in sporting goods. For this study, two global sports brands, Nike and Adidas, were selected, and brand stimuli (cartoons with scenarios) were designed based on a qualitative analysis of brand cases. A total of 207 usable responses were obtained from Korean consumers who had purchased the selected brands. The findings show that fashion brand authenticity consisted of seven factors: authority, fashionability, consistency, innovativeness, sustainability, origin, and heritage. Of these factors, authority, fashionability, innovativeness, and sustainability were significant predictors of brand attachment, and authority, consistency, and innovativeness were significant predictors of brand loyalty. There were differences in the effects of brand authenticity on brand attachment and brand commitment between Nike and Adidas. From a managerial and holistic marketing perspective, implications are suggested regarding the importance of managing brand authenticity in product innovation and management approaches.