This study analysed and compared the sustainability discourse on websites of fashion firms judged as high-rated or low-rated in sustainability ratings by an independent verification body using corpus linguistic techniques. We found that while both types of firms showcase their environmental and social performances to represent a sustainable image, they differ significantly in various aspects. High-rated firms proactively disclose details on workers’ wages and their environmental impacts and reveal hidden industry norms to drive a change from within the industry. Contrarily, low-rated firms are vague about disclosing details regarding workers’ wages and advocate consumer-driven and market-based solutions for industry problems, highlighting a multi-stakeholder approach. We argue that what separates high and low-rated firms regarding their sustainability discourse is their level of transparency (the amount of information disclosed for tracing delivery of promised goals) and their attitude towards industry-wide problems. We summarise a list of potential greenwashing indicators based on these findings.