Dysmicoccus lepelleyi (Betrem) is a quarantine pest on mangosteen. Its presence on mangosteen fruit can inhibit the exportation, resulting in the decreasing of state income from export activities. Gamma irradiation is an alternative treatment to eradicate D. lepelleyi on mangosteen. The aim of this study was to determine the lethal and the effective doses of gamma irradiation [60Co] in eradicating D. lepelleyi on mangosteen fruit and its effect on the quality of the fruit. During the experiments, the effects of sublethal dose was also observed daily up to 70 days after irradiation. The treatment doses started from 0 to 2,000 Gray (Gy) for all stages of life of this mealybug. The LD99 values of 1st, 2nd, 3rd instar nymphs and adult were 683.07, 1,329.10, 1,942.60 and 2,231.39 Gy, respectively. All females that survived from irradiation were sterile. Sublethal dose treatments on adult at 0, 200, 300, 400, 500, and 600 Gy still can produce eggs but 94.2–99.4% of the eggs could not hatch, moreover all the crawlers that hatch from the fertile eggs were dead. The sublethal doses were not affected the quality of fruits except the color at 600 Gy compared to the control. Based on this research, the effective dose that can be suggested is 200 Gy and can be used as a reference on quarantine treatment.