The rice weevil Sitophilus oryzae (Coleoptera: Curculionidae) is a significant stored product pest which attacks the seeds of several crops, including wheat, rice and maize. The present work was carried out to evaluate the effect of celery, camphor, and garlic oils on the main metabolites and several enzymatic activities in adults of rice weevil. Laboratory tests were conducted by treating wheat grains with plant oils. Treatment adults of rice weevil with the LC₅₀ values determined for the oils were found to be 0.8 ml/kg for celery oil, 0.85 ml/kg for camphor oil, and 1.27 ml/kg for garlic oil. All treatments resulted in a significant decrease in the contents of total proteins, lipids, and carbohydrates in the rice weevils. Additionally, varying levels of significant changes were observed in carbohydrate levels and the activities of enzymes such as protease, phosphatases, and acetylcholinesterase in the bodies of treated insects compared to the control group. These findings highlight the potential of using plant-derived oils as effective biopesticides against rice weevil.