The sweetpotato whitefly, Bemisia tabaci (Gennadius), is a pest that causes direct damage to host plants and also vectors plant viruses. Chemical insecticides are not always effective management tools because this insect has developed resistance to a wide range of insecticides. An essential oil from citronella (Cymbopogon nardus L.) leaves was assessed in studies of contact-toxicity, repellency, and ovipositional deterrence against B. tabaci. Mortality of B. tabaci exposed to the essential oil increased with the concentration of the essential oil with the greatest mortality observed at the highest concentration (6.66 μL/L air) tested (survival was reduced 94.3% in comparison to control treatments). The median lethal concentration was 1.028 μL/L air. Furthermore, the essential oil was highly repellent against B. tabaci in a dual-choice bioassay, and it significantly deterred females from laying eggs on essential oil-treated chili (Capsicum annuum L.) leaves as compared to control leaves. Chemical analysis of the oil was characterized by high levels of oxygenated monoterpenes (56.28%).