Leptocybe invasa Fisher & La Salle was first recorded several years ago in Sri Lanka in the Eucalyptus camaldulensis Dehnh. plantation in Maragamuwa. Recent observations have revealed a decrease in gall infestation, and the present study was conducted to investigate the biology of L. invasa, its damage to E. camaldulensis and the presence of any natural enemies. Life-cycle duration, developmental stages and activity patterns were investigated. The abundance of gall wasps was monitored using sticky traps. Damage caused to different stages of coppices was also assessed. The damage index was calculated from the percentage of leaves affected in each coppice. Insects were reared from the galled coppices, brought to the laboratory, identified and counted. The life-cycle duration of L. invasa was 132 days on average. The damage index was low throughout the study period. Leptocybe invasa attacked the coppices of E. camaldulensis when they turned green in colour; damage increased as the coppices developed until maturity. Four species of parasitoid wasps were reared from the leaf and shoot galls. Megastigmus sp. was the most abundant parasitoid; the mean percentage of parasitization was 67.00 ± 8.00. Natural enemies of L. invasa might have contributed to the decrease in gall infestation observed recently in the coppices of E. camaldulensis in the study site.