Rhinoderma darwinii lays eggs on damp ground in leaf litter. The male stays with the clutch for around three weeks. When movement begins inside the capsules, he takes the embryos into his mouth and they pass into the vocal sac, an air space normally used to amplify calls.
Inside the sac the larvae are nourished partly by their own yolk and partly by secretions from the sac wall. They complete metamorphosis there over roughly six to eight weeks, and the male eventually releases small but fully formed froglets. The behaviour is called neomelia, and only the two Rhinoderma species are known to use the vocal sac this way.
The closely related Chile Darwin's frog, Rhinoderma rufum, has not been reliably recorded in the wild since the 1980s and may be extinct. In R. rufum the male carried larvae only until they became free-swimming tadpoles, then released them into water, so the two species differ in how far the brooding is taken.