The fashion industry is gradually shifting from its dependence on a wasteful system towards the integration of increasingly sustainable practices. Accordingly, players in the fashion industry are beginning to communicate sustainability through channels such as Sustainability Reporting and Social Media. This study’s purpose is to explore the connections between annual Sustainability Reporting and Social Media by observing the way they convey Sustainability Communication. Each key concept of this study is researched at length by current academics, however, the combination of the three in the context of Sustainable Fashion is not well researched. Sustainable Fashion is understood as the next reality for the industry, embracing all aspects of the Triple Bottom Line, to overcome current challenges. Hence, engaging in Sustainability Communication and Reporting is a step towards transparency, in which the role of Social Media is growing. Studying Sustainability Communication through Social Media and Sustainability Reporting provides an idea of how Sustainable Fashion brands communicate their sustainability efforts. Two Swedish companies were observed, Dedicated and Lindex, both with a focus on elements of the Triple Bottom Line: Environmental and social sustainability respectively. The study was conducted with an explorative and abductive approach, through a Qualitative Content Analysis following two main parts: Firstly, analyzing the content of the brands’ sustainability reports, and secondly analyzing and categorizing the content of their Instagram posts. A final analysis examined contents from sustainability reports and Social Media to identify diverse Sustainability Communication practices. The main findings were discussed in line with the set purpose. First, the analysis suggested that Sustainability Communication is disparate from reports to Social Media. As Social Media was seldom used to disclose their sustainability practices, it was instead embedded in the brands’ identities. When sustainability practices were communicated on Social Media, only a portion reflected the reports’ contents. Second, it was observed that despite the different sustainability focus between the brands and the lack of mandatory reporting standards, the two approached Sustainability Communication similarly. Overall, according to the findings and supported by previous research, Social Media presents an opportunity for brands to communicate their complex sustainability activities in a simplified way. Harnessing it can potentially heighten transparency and make information accessible to most consumers. The managerial contributions of this study concern managers for Sustainable Fashion brands to understand and synthesize their Sustainability Communication on Social Media.