The mealybug Phenacoccus madeirensis Green (Hemiptera: Coccomorpha: Pseudococcidae) is recorded from Algeria for the first time. This pest was first detected in the summer of 2018 in private gardens in Salamandre, on the coastal side of Mostaganem City in north-western Algeria, feeding on three ornamental plants: Hibiscus rosa-sinensis L., Hibiscus syriacus L. (Malvaceae) and Cestrum nocturnum L. (Solanaceae). In October 2018, it was also found on Aloysia citriodora Palàu (Verbenaceae) growing near Hibiscus. The first samples collected had been attacked by hymenopteran parasitoids. Surveys of ornamental nurseries and greenhouses growing vegetables in the area indicate that, at present, P. madeirensis seems to be restricted to ornamental plants. More surveys over larger areas are needed to determine its distribution and the likely origin of its introduction to Algeria.