Pseudopostega adusta is a moth of the Opostegidae family. It was described by Walsingham, Lord Thomas de Grey, in 1897. It is known from the West Indies, from Cuba east to Dominica, south to Belize and Ecuador. It is also known from Costa Rica. The length of the forewings is 2.1–2.8 mm. Adults have been recorded in January, March to April and June.