The Critically Endangered Cacatua sulphurea abbotti is a unique subspecies of cockatoo, endemic to a single tiny Masakambing Island in Indonesia. Data procurement on the status and distribution of their wild population is necessarily urgent in order to determine the best conservation strategy for this species. Data were collected annually from 2008-2018 by a direct roost count method in a roosting tree. Only 10 cockatoos were recorded in 2008, but the number continually increased up to 22 birds in 2018 (42.86% increase in a decade). The population was distributed in about 71% of the total size of the island, concentrated in the north-western part with a density of 1.56 (~ 2 birds/km2) in 2008 which raised up to 3.44 (~ 3 birds/km2) in 2018. The zero trapping policy enforced by the local government was probably effective in preventing the population decline, although the population is still vulnerable due to nesting failure, presumably low genetic quality and habitat destruction.