<p><i>Callosobruchus maculatus</i> (F.) (Coleoptera: Chrysomelidae) is a key pest of stored legumes in sub-Saharan Africa, causing substantial postharvest losses. This study evaluated the combined effects of seed morphotype, seed size, resistance level, and botanical insecticides on the mortality of <i>C. maculatus</i> in stored cowpea (<i>Vigna unguiculata</i>) and Bambara groundnut (<i>Vigna subterranea</i>) under ambient laboratory conditions with fluctuating temperature and relative humidity in northern Cameroon. Three morphotypes per species, varying in seed size and resistance level, were treated with hexane, acetone, and methanol leaf extracts of <i>Ocimum canum</i> Sims (Lamiaceae) and methanol root extract of <i>Gnidia kraussiana</i> Meisn. (Thymelaeaceae) at 0.5–4&#xa0;g/kg, with neem seed oil as a reference. Treated seeds were artificially infested with 20 adult <i>C. maculatus</i>, and mortality was recorded over 1–7 days. Morphotypes differed significantly in physical traits and inherent susceptibility, with large-seeded resistant types such as Samira (cowpea) and Guidiguis (Bambara groundnut) showing enhanced protection. Mortality increased with dosage and exposure time, and hexane and acetone extracts of <i>O. canum</i> generally outperformed neem oil, while <i>G. kraussiana</i> was effective across morphotypes, including resistant and susceptible classes. Significant interaction effects among morphotype, botanical source, dosage, and exposure period were detected. These results indicate that seed traits can influence the efficacy of botanical insecticides. However, further studies under field storage conditions are required to validate these findings and assess their applicability in smallholder systems.</p>