We studied, under laboratory conditions, behavioural traits related to social interactions, parental care and communication in Hyloxalus toachi. This species is diurnal. Females spent most of their time maintaining and defending territories and were more territorial than ♂♂. Male vocalizations included long-range advertisement calls, two kinds of close-range courtship calls, aggression calls and sounds produced while attempting to clasp ♀♀. During body contact, ♂♂ and ♀♀ produced encounter calls. Preovipositional amplexus was cephalic and lasted 10–15 minutes. During terrestrial oviposition, the ♂ climbed onto the dorsum of the ♀ in an axillary position, but without clasping the ♀. Fertilization occurred as the eggs were deposited. When oviposition was completed, the ♂ left the ♀, while the ♀ remained close to the clutch for up to 5 hours. The mean clutch size was 11 eggs. Eggs had a mean diameter of 2·4 mm. The incubation time was 13–16 days. During that time, egg attendance and transport of tadpoles to water were performed exclusively by the ♂. Tadpoles were carried on the ♂'s dorsum for up to 5 days. The behaviours and features reported here are useful for interpreting trends in the evolution of dendrobatid behaviour.