Rapid body color change of animals in response to environmental stimuli has at least three biological functions: predation avoidance, thermoregulation, and intraspecific communication. We tested the hypothesis that Phelsuma kochi, a Madagascan giant day gecko that normally has a bright green body color, darkens its color to maximize its level of background matching so as to evade predation. Because recent studies revealed that some lizard species are able to eavesdrop on avian alarm calls and respond with antipredator behavior, we conducted a playback experiment of avian alarm calls to examine whether P. kochi recognizes alarm calls and changes its body color in response to them. We played back alarm calls and songs of a syntopically occurring passerine bird, Terpsiphone mutata, and white noise to free-ranging geckos. The geckos changed their body color quicker and darker in response to alarm calls than songs, and they tended to keep their dark coloration for a longer duration after the playback of alarm calls than that of songs or white noise. This result suggests that P. kochi is able to eavesdrop on alarm calls of syntopic birds and respond by darkening its body color to reduce its conspicuousness to predators.