The papaya mealybug, Paracoccus marginatus Williams and Granara de Willink, is a serious pest of many agricultural plants and ornamentals. It has spread throughout most countries of the Caribbean region, causing huge economic losses to papayas since 1994. This pest alert reports P. marginatus damaging papayas in Taiwan for the first time. Besides it also describes the fundamental biological data of P. marginatus, its existing host plants, and its distribution in Taiwan and around the world.