How is sustainability communicated on TikTok and Instagram between influencers and their consumers? To answer this question, we investigate posts by sustainability influencers and ask how they professionally or unprofessionally address ecological, economic, and social (“Triple Bottom Line”) questions; then, we analyse how consumers of this content, professionally or unprofessionally, engage with this content through ecological, economic, and social comments to express themselves in turn. To gather data for our qualitative content analysis, a starting sample of posts by five influencers who are active on Instagram as well as on TikTok was created. We continued with theoretical sampling to diversify our coding system. Our empirical findings show that regarding professionalism, the proportion of professional comments on Instagram is only slightly higher than on TikTok, however, the proportion of them being quite low in both networks. What is more, we find different communication styles across platforms which we call a conversation culture on TikTok and a single-statement-culture on Instagram with further differences in the communication of emotion.