The rice weevil, Sitophilus oryzae Linnaeus, 1763 (Coleoptera: Curculionidae), is a major pest of stored cereals worldwide that causes significant grain loss by feeding internally on seeds. In this study, we propose the use of an atmospheric pressure cold plasma generated from dielectric barrier discharge (DBD) as an emerging technology in insect pest management. Series of experiments were conducted to test the effectiveness of such plasmas on the lethality of adult S. oryzae by measuring the mortality rate and examining the biochemical markers that impact the insects. Plasma treatments (24 kV input voltage at frequency of 2.5 or 7.5 kHz) were carried out in He and Ar, used as carrier gases, with exposure time ranging from 30 to 120 s. Results showed a high level of mortality (60–100%) for each treatment, with a better efficiency observed when Ar was used as carrier gas. Furthermore, at the highest repetition frequency (7.5 kHz), equivalent to 60 W of electrical power consumption, the insecticidal efficiency reached 100% insect mortality at only 1 h after a 30 s plasma treatment. The mortality rate appeared to be correlated with a notable decrease in protein content and an increase in catalase enzyme levels within the insects’ tissue, indicating that insecticidal mechanisms involve oxidative stress. This study demonstrates that low-energy atmospheric cold plasma has detrimental effects on rice weevils and could be considered a promising tool for pest control in stored food, which will help reduce global dependence on chemical pesticides.