In Indonesia Planococcus citri is a species mealybug that infects robusta coffee berries, that are very detrimental for farmers. However, the use of chemical pesticides is known to have negative impacts on health and environment so that the search for natural insecticides is continuously being carried out. This study aims to determine the insecticidal effect of citronella plant (Cymbopogon nardus L.) extract against the mealybugs. Citronella extract was screened for its phytochemical content and then divided into several concentration levels, namely 0% (control), 5%, 10%, 15%, 20%, and 25% sequentially. The adult females of mealybug feeding on coffee berries, were chosen as the test animal in this study. Coffee berries were soaked in treatment solution for 10 minutes. After being air-dried, the coffee berries were put into glass jars and then infested with 10 imago mealybugs. The treatment was conducted for12th, 24th, 48th and 72th hours. Lethality rate of the insect then noted and the median lethal concentration (LC50) of the extract was determined using probit analysis. The results showed that plant extract of citronella contain flavonoid, tannin, alkaloid, phenolic, and terpenoid. The death rate of mealybugs increased with increasing concentration of extract. The median concentration of citronella extract on mealybugs also decreased with increasing exposure time, namely: 20.2, 12.4, 7.6, and 5.3% for exposure times of 12, 24, 48, and 72 hours, respectively. Thus, it can be concluded that citronella extract has slightly toxic properties and can be developed as a botanical insecticide for mealybug pests.