Annona squamosa (Annonaceae) is one of the economically most important magnoliid species in Asia due to its edible, creamy and sweetly aromatic fruits, commonly known as sugar-apples or sweetsops. Recently, an emerging weevil pest of this plant species has been reported in northern Vietnam, where the weevils can aggregate on the flowers and damage them, thus reducing the crop of fruits. Morphological examination of the weevils revealed them to represent an unnamed species of the genus Endaeus Schoenherr, 1826 (Curculionidae: Curculioninae: Ochyromerini), here described as E. inexpectatus Hsiao & Kojima sp. nov. The description and diagnosis of the species are supplemented with photographs of the habitus and salient structures. The study presents the first case of a species of Endaeus weevils, which usually pollinate Annonaceae, causing damage to the flowers of a cultivated species of this family. By providing a name for this weevil species, the study lays the foundation for future investigations into its interactions with the plant and possible control measures to limit its damage to the flowers.