The toxicity of cypress (Cupressus sempervirens) and howood (Cinnamomum camphora) essential oils, and its constituents to adult western flower thrips, Frankliniella occidentalis using leaf-dipping bioassay and vapour-phase toxicity bioassays. Both cypress and howood essential oils were toxic to western flower thrips. The most active principles were determined to be linalool, linalool oxide, cis-linalool oxide, trans-linalool oxide, camphor, and 1,8-cineole from cypress and howood essential oils. Linalool (24h LC50, 0.030 µg/cm2), linalool oxide (24h LC50, 0.036 µg/cm2), cis-linalool oxide (24h LC50, 0.043 µg/cm2), trans-linalool oxide (24h LC50, 0.045 µg/cm2), and camphor (24h LC50, 0.10 µg/cm2) were the most toxic. Potent toxicity was also observed with 1,8-cineole, a-pinene, d-limonene, a-terpinene, cinnamaldehyde, b-pinene, 3-carene a-terpineol, camphene, and terpineol (24h LC50, 0.33–0.65 µg/cm2). The spray bioassy of cypress and howood oil formulation (500 ppm) resulted in > 80% mortality toward western flower thrips population. Global efforts to reduce the level of toxic synthetic insecticides in the agricultural environment justify further studies on cypress and howood essential oil-derived materials as potential contact-action fumigants for the control of western flower thrips populations.