During the breeding season, the great hornbills become very vocal. They make loud duets, beginning with a loud ‘kok’ given about once a second by the mate, to which the female joins in. They form monogamous pair bonds and live in small groups of 2-40 individuals.
The female hornbill builds a nest in the hollow of a large tree trunk, sealing the opening with a plaster made up mainly of feces. In Khao Sok it has been recorder that they also make their nests in small cliff cavities (the only place they are recorder to do so). She remains imprisoned there, relying on the male to bring her food, until the chicks are half develop. The clutch consists of one or two eggs which she incubates for 38-40 days. They are long-lived, living for nearly 50 years in captivity.