Sustainability is a broad concept and sustainable consumption includes using products and services that not only meet consumer needs but also minimizes the use of natural resources. Brands use social media (SM) to engage with consumers as it enables the brand to build an emotional connection, hence a great platform to provide sustainability related messaging. Thus, using consumers’ online brand-related activities (COBRA) as the theoretical framework, the purpose of this study was to develop an understanding of how sustainable brands utilize SM platforms for organization sustainability communication. Instagram and Facebook were selected for their high-frequency usage and five sustainable fashion brands were evaluated. Seven hundred and twenty-seven sustainability-related posts and 66,821 comments were analyzed using a qualitative content analysis approach, an established and credible methodology. Three months of SM posts were compiled and examined. Data was coded systematically as deemed appropriate based on the qualitative content analysis approach and resulted in 20 sub-themes across eight thematic categories. The findings of this study provide implications for enhancing stakeholder engagement through (1) content strategy (e.g. video content in sustainability messaging), (2) imagery (e.g. the use of lifestyle content and influencers), and (3) messaging strategy (e.g. educational posts that provide insight into brands’ sustainability initiatives).