Toxicity of Ocimum suave (Wild basil) crude oil extract on C. maculatus and test on seeds’ viability, was determined in the laboratory using contact toxicity assay method of different concentration 0.02, 0.04, 0.06 and 0.08mg to 20ml of water and 0.00g/20ml of water (control). 20g of cowpea seeds were weighed into separate Petri dishes and 10 adult weevils were inoculated and replicated four times. Each treatment was observed for 96h and recorded after every 12h. The result indicated that the crude oil extract had significant difference (p0.05) in the germination of treated cowpea seeds (Vigna unguiculata L) compared to the untreated control, which shows that the seeds still remained viable. This result showed that O. suave crude oil is effective in the protection of cowpea against cowpea bruchid Callosobruchus maculatus.