Value co-creation has emerged as a critical challenge for fashion brands in the age of social media. Despite its importance, scholars have not adequately explored the role of social media marketing (SMM) in enhancing value co-creation (VCC) intentions among fashion brand consumers in mainland China. SMM encompasses five hierarchical elements: entertainment, customization, interaction, electronic word-of-mouth (EWOM), and trendiness. This study developed a theoretical framework based on attribution theory and employed the partial least squares–structural equation modeling (PLS-SEM) method to analyze the value co-creation process. The results indicate that SMM positively impacts brand loyalty (BL), brand trust (BT), and VCC. Furthermore, BT positively affects BL and VCC, while also serving as a positive mediator between SMM and BL and VCC. Finally, BL positively enhances the VCC intentions of fashion brand consumers. Our study's unique insights, derived from the attribution theory's advantage point, enrich the marketing literature. These findings also offer practical guidelines and tips for marketing managers seeking to optimize their SMM mix for VCC.