Some animals, including fish, beetles, spiders and butterfly chrysalises, have such shiny surfaces that they appear almost mirror-like. A compelling but controversial hypothesis is that a mirror-like appearance enhances camouflage by reflecting the surrounding environment. We tested the efficacy of mirror-camouflage in a complex terrestrial environment using field predation and human detection experiments. Both experiments used highly realistic mirror-green and diffuse-green models of Australian Christmas beetles, in their natural forested habitat. Of 1080 beetle models deployed at two independent forested locations, 9% were attacked but there was no difference for mirror or diffuse beetles. Similarly, there was no difference in attack frequency when beetles were deployed on open ground where mirror camouflage is ineffective. The human detection experiment required participants to wear eye tracking glasses and complete a time-limited search task for beetle models placed in the forest. Participants showed no difference in the success probability or latency to detect mirror beetles. Taken together, our results suggest that the extremely shiny appearance of Christmas beetles does not reduce the probability of detection or attack by predators. Instead, highly shiny surfaces may have evolved as a secondary consequence of selection for a non-visual function, such as water repellency or cuticle strength.