Breeding occurs at the onset of the summer rains, from September to December, when there is greater food abundance. The birds nest in sizeable cavities high in large trees, rock faces or earth banks. The female does not seal herself into the nest or moult like other Hornbill species. Rather she stays in the nest for the majority of the nesting period, only leaving to defecate and to perform the territorial calls with the rest of the group.
Copulation occurs between the alpha female and alpha male. During this period, the group will line the nest with grass and leaves. The remaining helpers, consisting of juveniles, sub-adults and adults contribute towards the breeding process by feeding the female and the subsequent in the nest. Juveniles from the previous season rarely, if at all, help with food provisioning, but are often present at the nest begging for food from the adults as they are still largely reliant on their care.
The female will lay two eggs in a clutch (around 80% of the time). These eggs are laid three to five days apart and are incubated for about 40 days. The different laying times for the eggs means that the chicks hatch at different times and inevitably, the older chick outcompetes the younger one. The second-hatched chick is younger and smaller and succumbs to dehydration within a few days . This second chick acts as an insurance policy, so that if the first chick does not survive or the first laid egg fails, it will then successfully be raised by the group. The raising of two chicks has never been recorded in the species.
The successful Southern Ground-Hornbill chick remains in the nest for around 80 to 90 days, where it is fed and cared for by the group. Upon fledging, the chick is almost fully developed weighing around three to four kilograms. The beak, however, is still considerably smaller than the adult birds and continues to grow as the young bird matures.