Around 5–20% of the total banana crop in the Philippines is rejected because it does not meet the specifications for export as fresh fruit. This study aimed to utilize the out-of-specification unripe Cavendish banana of local exporters into banana powder. The effects of different pre-drying treatments such as blanching time and concentrations of citric acid and ascorbic acid on the properties of the resulting Cavendish banana powder in terms of moisture content, water activity, color, solubility, water absorption capacity, bulk density, water holding capacity, and % yield were determined using a central composite face-centered response surface methodology design. Significant mathematical models were generated that predicted the effects of individual and combined influences of pre-drying treatments. Results showed that ascorbic acid was the main factor that influence the lightness, water activity, swelling power, bulk density, and water absorption capacity of banana powder. Results of the optimization process suggested that the desirable pre-drying treatments for banana powder were a blanching time of 0–5 min, as well as soaking in ascorbic acid ranging from 0.01–0.10% and in citric acid ranging from 0.07–0.10%. The identified optimal treatment ranges for blanching time, ascorbic acid concentration, and citric acid concentration provide valuable insights for producing acceptable, safe, and high-quality banana powder. By utilizing out-of-specification bananas and transforming them into value-added intermediate products like powder, the banana industry can reduce waste, maximize resource utilization, and create a more environmentally friendly and economically viable approach to banana production.