Thirteen cowpea varieties and two cereal grains were evaluated in the laboratory for their susceptibility to Sitophilus oryzae (Coleoptera: Curculionidae). Parameters used in this evaluation were damage and losses caused to grains that were attacked, and the suitability of the grains for insect breeding. Results showed that S. oryzae caused varying degrees of damage and weight loss to eight varieties of cowpeas, just as it did to sorghum and maize. Five varieties of cowpea (IT86D-719, IT86D-721, IT89KD-288, IT90K-277-2 and IT93K-452-1) were significantly (P < 0.01) resistant to S. oryzae than other varieties of cowpeas. SARC-L02 had significantly (P < 0.05) higher susceptibility index while IT90K-277-2 had the lowest susceptibility index of zero. In the absence of its preferred host crop, sorghum or rice, S. oryzae will most probably switch host to cowpea instead of maize, because it developed faster on most cowpeas, just like it does on sorghum than on maize. This unusual observation calls for urgent integrated action on grain handling and storage, as many are often stored together in markets or stores by grain dealers and farmers and this would increase the risk of easy spread of the weevil in such stores.