Black-fronted Terns (Sterna albostriata) are an endangered species endemic to New Zealand whose breeding biology and survival are poorly understood, yet the species is in urgent need of management. I studied aspects of Black-fronted Tern breeding ecology and survival on the Ohau River, South Island, New Zealand, from 1998 to 2001. Over three breeding seasons, 50.2% of 1022 nests successfully hatched one or more eggs. Predation (24.6%) and desertion (21.4%) were the main causes of nest failure. At least 28% of all hatched chicks (n = 897) survived to fledge. Productivity for each of three breeding seasons was estimated at 0.23, 0.34 and 0.27 fledglings per nest. Hatching and fledging rates at individual colonies ranged widely, largely because of the impacts of predation by introduced mammals. Evidence from video cameras placed at nests suggested predators were a cause of nocturnal and permanent desertion of both eggs and chicks, and that single predators could destroy entire colonies. Based on re-sightings of 72 colour-banded adult Terns, adult annual survival rate was estimated at 0.88–0.92 but the associated confidence intervals were wide (0.57–0.99). Most re-sightings (77%) of banded adults that were nesting were either in the colony in which they were banded or elsewhere on the Ohau River. This is the first comprehensive study on the breeding biology of Black-fronted Terns and indicates that predator control is essential to the future survival of the species.