Visually aposematic prey warns their potential predators about their noxious condition by exhibiting conspicuous coloration. The larvae of some phyllomedusine frogs bear bright patches on the body or tail that suggest an anti-predator role, yet the experimental evidence of aposematism in anuran larvae is notoriously scarce. Here, we assessed and compared the conspicuousness and skin toxicity of three species of phyllomedusine larvae which differ in coloration: Phyllomedusa vaillanti, P. bicolor, and Callimedusa tomopterna. The conspicuous colorations found on the dorsal area of the larvae could be directed to aerial predators, therefore we evaluated the distribution of the larvae in the depth of the water column. We also experimentally assessed their palatability to dragonfly naiads as model predators. Additionally, we observed that all these traits that make up the antipredatory syndrome are modified along the ontogeny of the larvae. For this reason, we assessed body size as another trait that conforms to the syndrome. Our results support an antipredatory syndrome in larvae of P. vaillanti and to a lesser degree in P. bicolor. The most conspicuous larvae were indeed the most toxic. Moreover, these larvae were attacked less often by predators which, in turn, died within a few hours. In both species, the larvae remained close to the water column surface longer to advertise their noxious condition towards predators. After we included body size in the anti-predator syndrome, we observed that only the P. vaillanti larger larvae were more conspicuous. Toxicity and palatability were not related to body size. Nevertheless, vertical distribution varied ontogenetically in P. bicolor. The largest larvae remained close to the water surface most of the time, while the small ones were distributed evenly throughout the water column.