<p>Background matching is a common form of crypsis in animals, resulting from selective pressures imposed by visual systems of predators and/or prey. Therefore, it could be expected that novel backgrounds would pose a barrier to the establishment of invasive species, due to a lack of crypsis. Behavioural flexibility in crypsis—through facultative crypsis and/or choice of matching backgrounds—has been suggested as a trait that may facilitate invasiveness. We assessed background-matching and facultative brightness-change in an Australian population of the invasive Asian House Gecko (<i>Hemidactylus frenatus</i>). This species is currently expanding from urban environments into surrounding tropical woodland, and demonstrates great variability in colour and pattern among individuals. We quantified wild background-matching in terms of both colour and brightness. We then experimentally tested whether geckos facultatively change brightness in the direction expected for a given background. <i>Hemidactylus frenatus</i> consistently brightness-matched across the backgrounds on which they were found, more than would be expected by chance. Experiments showed that <i>H. frenatus</i> rapidly changed in their dorsal brightness, in the direction expected given their background, suggesting that brightness-matching observed in wild geckos is due to facultative brightness-change. Successful invasion may benefit from facultative crypsis; however, it remains to be demonstrated how facultative brightness-change in <i>H. frenatus</i> is linked to predation and invasion success. We outline how recognition of facultative colour-pattern change in invasive species may be important for early detection and management actions.</p>