Four plant essential oils alone as repellent and fumigant, and in combination with the controlled modified atmospheres against the adult of cowpea weevil, Callosobruchus maculatus Fabricius (Coleoptera: Bruchidae) were assessed in the laboratory. These essential oils were extracted from the leaves of four source plants: Prunus amigdalus, Moringa oleifera, Simmondsia chinensis, and Ricinus communis. The repellency test indicated that C. maculatus adults were repelled by four essential oils. Of these essential oils, the P. amigdalus oil was most effective followed by M. oleifera, S. chinensis, and R. communis. The average repellency of the P. amigdalus oil against C. maculatus adults was significantly higher than the other three tested oils after 7 days. These essential oils had a high level of toxicity in the fumigation assay against C. maculatus adults. The results showed that P. amigdalus oil gave the highest toxicity at LC₅₀ (2.08 ppm) and R. communis gave the lowest value of LC₅₀ (55.05ppm). In results of the effectiveness of the four essential oils when combined with two controlled atmospheres concentrations, 12.5- 25% CO₂, the toxicity of plant oils was enhanced significantly against C. maculatus adults. The results of joint toxic action indicated that at concentration 10 ppm of the four essential oils under modified atmospheres of 12.5 % CO₂ produced an additive effect at all exposure periods, while in case of M. oleifera and S. chinensis gave additive effect at 3 and 5 days exposure periods. The same trend was found at the highest concentration 20 ppm of three essential oils P. amigdalus, M. oleifera, and S. chinensis under modified atmospheres of 12.5-25% CO₂ and produced an additive effect at all exposure periods, while Co-toxicity values of 20 ppm R. communis essential oil after the various exposer periods showed antagonism effect against C. maculatus adults. In conclusion, the present study revealed that the combination of the four tested essential oils with CO₂ enhanced its fumigant toxicity to stored product insect, cowpea beetle.