The present work aimed to evaluate the effect of fermentation by Rhizopus oryzae on the proximate composition, anti-nutrient contents, and functional properties of banana peel flour using the solid-state fermentation method in a tray bioreactor at 30°C for 96 h. Throughout fermentation, samples were obtained at different times (0/NF, 24, 48, 72, and 96 h), and analysed using standard procedures to determine the proximate composition, anti-nutrient contents, and functional properties. Based on the results, there were significant differences observed (p < 0.05). Carbohydrate content decreased by 3.35%, while the crude protein, fat, ash, and crude fibre contents increased by 11.12, 2.43, 10.99, and 3.50%, respectively. Hydrogen cyanide, saponin, oxalate, and phytate contents decreased by 42.59, 25, 23.83, and 43.82%, respectively. Water absorption capacity (WAC) and the water solubility index (WSI) increased by 3.94 and 37.14%, respectively, while oil absorption capacity (OAC) decreased by 4.48%. These results showed that the fermentation of banana peel flour by R. oryzae has potential benefits for the food industry due to its effect on chemical composition and functional properties.