Eucalyptus species are widely planted for their rapid growth, high timber and commercial cellulose fiber. Several Eucalyptus pests have spread around the world, generally without their natural enemies. The present study was carried out on Madagascar and the Mascarene islands (Mauritius and Reunion), located in the southwestern Indian Ocean, on new eucalypt pests, their natural enemies and the infestation levels of the main pests Glycaspis brimblecombei, Leptocybe invasa and Ophelimus maskelli. By combining morphological and molecular identifications, we newly reported Blastopsylla occidentalis, Closterocerus chamaeleon and the genus Psyllaephagus on the three islands; Aprostocetus spp., Ctenarytaina eucalypti, O. maskelli, Quadrastichodella nova and Quadrastichus mendeli on Reunion; Megastigmus zebrinus on Madagascar; and the genus Aprostocetus on Mauritius. We also confirmed the presence of G. brimblecombei, L. invasa and Thaumastocoris peregrinus on all three islands, O. maskelli on Madagascar and Mauritius and Q. mendeli on Mauritius. Through a thorough review of the literature, we investigated Eucalyptus pests, their associated parasitoids and the damage they can cause. On the Madagascar and Mascarene islands, we highlighted the presence of the C. chamaeleon and Psyllaephagus genera, the natural enemies of O. maskelli and Psyllidae species, respectively. Moreover, the high population level of L. invasa seems to affect the survival of Eucalyptus in Madagascar. Leptocybe invasa appears to be regulated by Q. mendeli in Mascarene but not in Madagascar. Given the damage caused by L. invasa to malagasy Eucalyptus, introducing Q. mendeli could be considered a means of biological control in Madagascar.