Four underutilized plant seed oils Thevetia peruviana (TP), Hura crepitans (HC), Sesamum indica (SI) and Mangifera indica (MI) were converted to fatty acid amides by reacting concentrated ammonia with acid chloride. The conversion was monitored and confirmed with sodium fusion test, fourier transform infrared (FTIR) and 1H NMR and 13C NMR (Nuclear Magnetic Resonance). The result of the antifungal test against Fusarium solani, Sclerotium rolfsii, Pyricularia oryzae and Cyrtomium falcatum showed that all amides are potential antifungal agents. In contrary; the results obtained for antibacterial test showed little or no inhibition of these bacterial strains (Staphylococcus aureus, Escherichia coli, Xanthomonas spp., Pseudomonas syringae and Bacillus subtilis) at 15 mg/mL.