Social media have surged prominently as communication channels for corporate social responsibility. However, little is still known about the performance of green versus non‐green communication across different social media. We contribute by examining whether the presence of green features in social media communication exerts a beneficial effect on consumer response in terms of likes, comments, and shares. We also investigate how this effect hinges upon the social media platform where the content is posted as well as the richness of the format (text, photos, videos) utilized for the diffusion. To our scopes, we use an ad hoc dataset of posts of two major large‐scale retailers in Italy across three major social media, namely Facebook, Instagram, and Twitter. Our results show that, while green content generally stimulates larger response than non‐green content, its effect varies across social media, with the highest effect being observed on Instagram (at least for likes) and the lowest on Twitter (at least for comments). Moreover, the extent to which the positive effect of green content increases as media richness increases (i.e., moving from only text to text plus photo, and then to text plus video) is also contingent upon the social media platform. On Facebook, the moderation of media richness is positive and significant, while being insignificant on Instagram. On Twitter, the moderation is even nonmonotonic in the sense that the highest (positive) effect of green content tends to be obtained for either low or high media richness. Our findings offer remarkable implications for firms engaging in environmental sustainability.