The chemical composition of the essential oil extracted by hydro-distillation using Clevenger apparatus from aerial parts of Thuja orientalis and Eucalyptus camaldulensis grown in Ondo State, Nigeria was analysed by Gas Chromatography/Mass Spectrometry technique. Toxicity of the essential oils using anti-feedant and filter paper methods on Callosobrochus maculatus was also carried out after 6 and 24 hours application. Antibacterial and antifungal activity against ten pathogens which are Escherichia coli, Salmonella paratyphi, Bacillus subtillis, Staphyclococcus aureus, Klebsiella pneumonia, Streptococcus pneumonia as bacteria and Aspergillus niger, Aspergillus flavus, Candida tropicallis and Fusarium solari as fungal were carried out. The results of the GC-MS showed that twentythree compounds representing 93.73% of total oil of T. orientalis with α-pinene (32.93%), Δ-3-carene (20.43%), benzyl alcohol (8.69%), myrcene (8.18%), α-terpineol (6.01%) and limonene (5.02%) as the major components. Also, five components which constituted 97.37% of the total oil of E. camaldulensis were identified with 1,8-cineole (73.94%), Limonene (9.22%), Cymene (5.90%), Geraniol (5.20%) and α-pinene (3.11%). The results of the toxicity of the Essential oils showed that 100% mortality were recorded for antifeedant of both plants, except at 0.1mL/g concentration for T. orientalis which has 96.7% and that of filter paper ranged between 83 to 100% for T. orientalis and 70 to 100% for E. camaldulensis.