Alien species can influence populations of native species through individual-level effects such as predation, competition, and poisoning. For alien species that possess strong defensive chemicals, poisoning is one of the most powerful mechanisms of individual-level effects on native biota. Although toxic alien species could potentially negatively affect survival (lethal effects) or life history traits (sublethal effects) of native predators via poisoning, previous studies have mainly focused on acute lethal effects. Thus, delayed effects on predator life history traits have been largely overlooked. To fill this knowledge gap, we conducted laboratory and field experiments to investigate whether toxic alien prey (hatchlings and tadpoles of an invasive toad, Bufo japonicus formosus) affect survival and/or growth and development of a native predatory salamander (larvae of Hynobius retardatus) on Hokkaido, Japan. The laboratory experiment revealed that consumption of a single toad hatchling exerted no lethal effects on salamanders, but suppressed both salamander growth and development of an ecological phenotype (broad gape) normally induced by environmental conditions. Furthermore, the field experiment in a natural pond showed that the presence of toad hatchlings and tadpoles resulted in reduced salamander growth (smaller body size) and lower survival of salamanders in the later larval period. The results of the laboratory and field experiments are complementary evidence of the life history impacts of the toxic alien toad on native salamanders. Thus, poisoning effects of toxic alien species can affect the life history of native predators even if they do not exert the acute lethality.