This chapter examines the mechanisms underpinning sustainable fashion consumption, providing a nuanced understanding of how cognitive, emotional, and social factors shape consumers’ fashion choices. It begins by contextualising the fashion industry’s unsustainability and the barriers hindering ethical consumption. Drawing on cognitive psychology, the chapter explores how impulsive tendencies, attitudes, norms, and perceived behavioural control contribute to the persistent attitude-behaviour gap. It further delves into intra-individual variables such as personality traits and fashion orientation, highlighting their complex influence on consumption. Social dimensions including peer influence, cultural norms, and consumer segmentation reveal how collective dynamics and digital environments shape sustainable fashion engagement. The chapter concludes by evaluating strategies like nudging, educational campaigns, policy interventions, and marketing innovations that promote sustainable practices. It calls for future research to assess policy impact, cross-cultural differences, and the emotional and identity-driven dimensions of fashion behaviour. Through a multidisciplinary lens, the chapter proposes a shift towards reflective thinking to foster meaningful, sustainable change in fashion consumption.