Numerous designer luxury brands have been interested in creating co-branding partnerships with the fast-fashion retailer H&M. Despite the recognition by some researchers of the value of examining whether consumer reactions to the co-partnering luxury brands will be affected by the collaboration, to the best of our knowledge, no research to date has examined luxury consumer reactions to such partnerships. Accordingly, this research specifically explores how the collaboration between a luxury brand and a fast-fashion brand impacts on consumer reactions to the luxury brand. Considering the exploratory nature of this study, thirty face-to-face in-depth interviews were conducted in the UK to reveal insights into consumer reactions, given the limited knowledge on the subject matter. Six themes emerged from this study: (a) enhanced brand awareness, (b) impaired perception, (c) word-of-mouth, (d) consumer engagement, (e) perceived self-expressiveness and (f) brand avoidance.