The Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos) breeds only at the Tristan da Cunha archipelago and Gough Island in the central South Atlantic Ocean, and is threatened by mortality from longline fisheries operating in the South Atlantic. Demographic data have been collected from two study colonies on Gough Island and Tristan da Cunha for 20 years. Annual variation in the number of breeding birds was strongly correlated between the two islands, and over the whole study period both study populations have trended downward at around 1.2% per year. The number of established breeders on Gough Island has declined more rapidly, and significantly, at an annual rate of 2.3%. Monitoring established breeders maybe a sensitive means of detecting population trends. Average breeding success (67–69%) and breeding frequency (66–65%) were very similar on the two islands. On Gough Island immature and adult annual apparent survival averaged 88 ± 3% and 92 ± 1%, respectively, and apparent survival from fledging to age 5 has averaged 31 ± 8%. Apparent adult survival on Tristan da Cunha averaged only 84 ± 2%. Annual survival of Tristan birds was negatively correlated with longline fishing effort in the South Atlantic Ocean. Population modeling predicts annual rates of decrease of 1.5–2.8% on Gough Island and 5.5% on Tristan da Cunha. Comparison with congeners suggests that the observed and predicted decreases are most likely to be caused by low adult and immature survival. The conservation status of Atlantic Yellow-nosed Albatrosses should be changed from Near Threatened to Endangered.