Despite the evolution of luxury fashion and the emergence of new consumer profiles and behaviours, research has predominantly focused on the traditional consumption of brand-new luxury goods. In contrast, this chapter seeks to advance knowledge on an emerging consumer segment within the luxury industry: the second-hand luxury fashion consumer, as a contemporary and valuable topic worthy of exploration as we examine new horizons in fashion consumption and marketing. We define terms such as second-hand luxury fashion and conscious consumption via a sustainably sartorial framework. We examine and critically review the current literature on self-determination theory (SDT) as a motivational and theoretical lens that advances the understanding of this consumption phenomenon. We propose a set of motivational archetypes to understand better this emerging sustainable fashion segment and its potential impact on our understanding of fashion marketing and consumption as a new horizon in fashion consumerism.