Attitude, Environmental Concern, and Self-Efficacy as Drivers of Purchase Intention: The Role of Dupe Product Availability in Sustainable Fashion Purchase Behavior in Indonesia

Despite Indonesia's high willingness to pay a premium for sustainable products, sustainable fashion consumption remains limited by a persistent intention–behavior gap, further complicated by the growing availability of low-priced dupe products. Grounded in the Extended Theory of Planned Behavior (E-TPB), this study examines the determinants of sustainable fashion purchase intention and whether perceived dupe product availability moderates the intention–behavior relationship among Indonesian Millennial and Generation Z consumers. A quantitative survey of 264 respondents in the Jabodetabek metropolitan area was analyzed using Partial Least Squares Structural Equation Modeling (PLS-SEM). The measurement model met all reliability and validity requirements. The findings show that attitude (β = 0.323), self-efficacy (β = 0.202), and environmental concern (β = 0.178) significantly influence purchase intention (R² = 0.533), whereas environmental knowledge, subjective norm, and perceived behavioral control do not. Purchase intention significantly predicts purchase behavior (β = 0.426, R² = 0.322). However, perceived dupe availability does not moderate the intention–behavior relationship (β = 0.028, p = 0.425) but has a significant direct effect on purchase behavior (β = 0.307, p < 0.001). These findings suggest that dupe products act as an independent competing alternative, providing theoretical insights and practical implications for sustainable fashion marketing strategies.