Studies on antifungal effect of garlic (Allium sativum) essential oil and wood ash were determined on causative agents of post-harvest fruit rot of banana. Different concentrations of essential oil of garlic (0.15, 0.50, and 1.0%) and quantities of wood ash (0.1, 0.3 and 0.5g) were used. The treatments were laid out in Completely Randomized Design (CRD) with three replications. Four (4) fungal pathogens associated with rots of banana fruits were isolated. The fungi isolated and their incidence of occurrence included Colletotrichum musae (18%), Pyricularia grisea (18%), Rhizoctonia solani (38%) and Rhizopus stolonifer(26%). Rhizoctonia solani and Rhizopus stolonifer were the most pathogenic with rot covering more than 75% of the fruit surface. All the tested concentrations (0.15, 0.5 and 1.0%) of essential oil of garlic significantly (p < 0.05) suppressed mycelial growth of the fungi in-vitro. Also all tested quantities of wood ash (0.1, 0.3 and 0.5g) significantly (p < 0.05) reduced the rots of the fungi in-vivo. The effect was proportional to the concentrations of essential oil of garlic and quantities of wood ash used and reduction was highest at 1.0% of garlic oil and 0.5g of wood ash. Both garlic (Allium sativum) essential oil and wood ash proved effective in the control of disease severity and these natural plant materials are recommended as an alternative to pesticides which are often harmful and costly.