Bioassay of ethanolic crude extract of Mundulea sericea (Willd.) A. Chev. (syn. M. suberosa Benth.) was compared with the leaf powder for their insecticidal potential against Callosobruchus maculatus on stored cowpea using actellic (25 EC) and actellic (2 %) as standard checks with an untreated control. Five pairs of day old adult C. maculatus were sexed and used to infest 100 g IAR-48 (SAMPEA 7) cowpea seeds stored for three months containing 1, 2 and 3 ml or g of the treatments with each replicated three times. All treated jars were shaken thoroughly to ensure effective coating of seeds with treatments and left on laboratory benches in the Storage Entomology Laboratory of Crop Protection Department, Institute for Agricultural Research(IAR)/Faculty of Agriculture, Ahmadu Bello University, Zaria under open conditions of 28Â± 2OC and 70Â± 10 % relative humidity. Insect mortality, oviposition, progeny emergence as well as percentage seed damage and viability were assessed. The results revealed that, the plant materials like their synthetic counterparts (Actellic 25 EC and 2 % dust) significantly (P less than 0.05 %) caused higher insect mortality, reduced oviposition and inhibited progeny emergence with not much damage to seed integrity and viability. Though both plant materials were found to be effective in protecting cowpea seeds against C. maculatus attack however, the Mundulea ethanolic extract was significantly better than the dust which was in turn better than the untreated control but was not as good as the synthetic pesticides.