The chapter explains sustainable fashion consumer behavior based on the Theory of Planned Behavior (TPB) and its extensions as purchase decision psychological and social determinants theoretical models. The study examines the effect of attitudes, subjective norms, and perceived behavior control on young customers’ purchasing intentions for sustainable fashion products. This chapter provides an integrated theory of sustainable consumption motives by expanding the TPB model to settings such as control beliefs, normative beliefs, and behavior beliefs. It also addresses how individual beliefs, moral norms, and society influence consumer behaviors. The findings of the present study are generalizable to companies that want to offer sustainable fashion because they represent a chain of cognitive rules, emotional experiences, and self-concept in regulating pro-environmental consumer behavior. This chapter adds to sustainable consumer behavior scholarship and is business relevant for the fashion industry in motivating more sustainable consumption behavior.