Major fast fashion companies have recently launched resale platforms for second-hand shopping. Although experts consider these initiatives as a greenwashing strategy, it is unclear whether consumers agree with that or rather find such initiatives sustainable. Thus, the purpose of this paper is to examine consumer attitudes towards the sustainability of second-hand fast fashion. Accordingly, Instagram reels and posts related to second-hand fast fashion are identified and all comments under those contents are extracted. Next, these comments are analysed with a sentiment analysis and a content analysis. Results show that consumers express more positive sentiments towards resale companies that ban fast fashion items than towards resale companies that specialize in fast fashion. Comments referring to companies banning fast fashion resale show consumers’ predominant support of the ban, while companies doing fast fashion resale receive strong criticism on social media. Consumers are specifically concerned about the quality of second-hand fast fashion items as well as express social and ethical concerns towards fast-fashion resale. The resulting practical implication is that companies should consider discontinuing second-hand fast fashion.