Anurans are key prey for snakes, and their decline can affect snake diversity. Defensive behaviors in frogs are diverse and include secretions, distress calls, and body inflation. Frogs of the genus Trachycephalus, known as “milk frogs,” produce sticky and potentially toxic secretions. Predation events involving these frogs are rarely documented. We observed an adult parrotsnake Leptophis mystacinus preying on an adult treefrog Trachycephalus mambaiensis in a Cerrado–Caatinga transitional area in Minas Gerais, Brazil. The frog briefly escaped but was recaptured and ingested within 10 minutes. This is the first documented case of L. mystacinus preying on T. mambaiensis. Although Leptophis species are known to prey primarily on hylid frogs, little is known about the diet of L. mystacinus. This observation supports its potential specialization on nocturnal treefrogs and suggests that it may use both visual and olfactory cues to detect inactive prey during day.