The fashion industry is one of the most challenging sectors for sustainable development, comprising numerous social and environmental challenges. The industry is based on a complex network of global and fragmented supply chains leading to a lack of transparency. Therefore, transparency and supply chain traceability are core priorities in order to increase the fashion supply chain visibility and enable accountability. A potential solution to this issue is the application of new technologies. Blockchain is an emerging technology that has a potential to address the current issues and make supply chain processes more transparent. The combination of the emerging blockchain technology with the concept of transparency in fashion supply chains constitutes the novelty of the research and the contribution to the current body of knowledge. The environmental and social challenges regarding transparency in fashion supply chains are analysed using the theories for Green Supply Chain Management and supply chain power structures. The study relies on interviews with blockchain professionals and industry experts in supply chains and sustainable fashion. The study finds that blockchain has the potential to become the single source of truth for the fashion supply chain and provide transparency across the supply chain. However, this advancement of transparency can only occur in a less complex fashion supply chain with a balanced power structure and more collaboration than the current standard.