Influencer marketing on social media plays an increasingly vital role in the overall marketing strategies for travel products. Previous research suggests that while traditional celebrities create value through exclusiveness, Social Media Influencers (SMIs) establish their value through authenticity and connectedness. However, exactly how they convey their authenticity is not well researched. Drawing on signalling theory, this study investigates the effect of SMI popularity (using the size of the following as a proxy) on consumers’ purchase intention as an outcome of authenticity perception, considering the moderating role of SMI’s perceived motive. A between-subjects design was employed, with participants (n = 236) randomly assigned to one of the two experimental conditions. Data were analysed using ANOVA and PROCESS Macro. Findings from our study suggest that consumers see micro SMI endorsers as more truthful, genuine, and authentic, which leads to greater intention to purchase the travel product. The effect of SMI popularity on authenticity perception is stronger for those who believe that SMIs are generally self-serving when they endorse products. This research has important ramifications for managers in the selection of SMI endorsers of their travel products. It also has implications for influencers who endorse products on social media.