The fashion industry is among the most polluting sectors worldwide. Each year, more than 92 million tons of textile waste are generated globally, while the number of wears per garment continues to decline. In the Netherlands, on average a person owns approximately 173 clothing items, purchases about 46 new items annually, and leaves roughly 50 pieces unworn in their closet. Overconsumption not only intensifies environmental pressures, such as excessive water use and rising CO₂ emissions, but also perpetuates social injustices embedded in production chains. In response to these trends, the United Nations, through Sustainable Development Goal #12, calls for cleaner production processes as well as fundamental shifts in consumer behavior. Sustainable fashion has emerged as a key pathway toward change, promoting ethical production and alternative consumption models such as resale, rental, and recycling. Retailers, positioned to shape consumer behavior, play a pivotal role in this transition but continue to struggle against the convenience and low prices of fast fashion. The central research question addressed by this dissertation is: How can sustainable fashion retailers apply insights into socio-psychological predictors of sustainable fashion consumption in their marketing tactics to encourage uptake of sustainable fashion? This dissertation comprises four studies: i) a systematic literature review on socio-psychological predictors of sustainable fashion purchasing; ii) a qualitative study on the perceptions and marketing tactics of sustainable fashion retailers; iii) an analysis of how second-hand fashion retailers cater to Generation Z; and iv) an experimental study on the influence of referral rewards on Generation Z purchase behavior.
