Although many synthetic pesticides have played important roles in pest management in agriculture, forest, housings, gardens, and managed landscapes for several decades, increased concerns to human health and environmental contamination have limited their usages and application in integrated pest management (IPM). Many plant essential oils have a variety of biological activities including adulticidal, acaricidal, larvicidal, ovicidal, repellent, antifeedant, and oviposition deterrent ones against insect pests. These oils and major terpenoid constituents show neurotoxic effects by interference with the cockroach octopamine and nematode SER-2 tyramine receptors. Most plant volatile oils contain plentiful phenylpropanoids, mono and sequiterpenes, and related phenols. They have been widely used in the flavor, fragrance, aroma therapy, food additives, and cosmetic industries. Some volatile plant essential oils have traditionally been used as stored product protectors and mosquito repellents, while their successful cases in commerce have been recently applied. Especially, these essential oils have not only been treated against house and garden pests, but these oils also have higher potential to be employed as “green pesticides” in the field of stored products, green house, and medical insect pests due to their fumigant action. Eventually, considering resistance development to many synthetic pesticides, it is likely that plant volatile or essential oil-based pesticides would play an essential role as an alternatives since they typically consist of the complex mixtures of constituents responsible for slow resistant development. In addition, the mixtures of these oils with conventional insecticides and the application of their capability to to enhance the efficacy of conventional products remains a main market niche. In this presentation, several cases of test evidences under laboratory and field conditions will be discussed. Ultimately, plant volatile-based pesticides and repellents would play an important role in future IPM programs due to their relative safety to non-target organisms and the environment.