Starting from the concept of sustainability in fashion, the aim of our research is to analyse to what extent the Zara Join Life collection is sustainable, environmentally friendly (as advertised), and transparent, in terms of the information provided to the consumer, in order to offer Zara’s fashion consumers a set of aspects to take into account when intending to buy responsibly, such as the composition of the product, the percentage of recyclable materials used, its origin, etc. Our practical goal is to generate a gradual change in Zara consumers’ behaviour by creating a set of basic skills to transform one from a fast, superficial consumer into a slow, conscious customer with decision-making power. We analysed the Zara Join Life collection, which is advertised on the company’s website as supporting sustainability as a continuous project. The methodology consisted of a documentation-learning stage in order to reach the stages of data collection, data processing, and information organization—the methods used for the analysis of fashion consumers’ behaviours. The analysis was conducted on 40 Zara Join Life collection garments (10 women’s clothing items, 10 men’s clothing items, and 20 garments for kids, both girls and boys) sold online on Zara’s website. The collected research data were analysed and interpreted within the case study.