Fifteen percent of harvested bananas are discarded daily in the Canary Islands at packing houses because of marketing standards, mainly based on their appearance, or are retired to avoid falls in the market price of bananas. This discarded fruit is an environmental issue, and green banana flour (GBF) is an interesting management alternative for it. In this paper, the artisanal process for obtaining GBF was optimized. The study of physicochemical and nutritional characteristics of this gluten-free flour indicated a high contribution of starch, fiber, phenolics, K, and Mg to dietary intake. Storage of GBF at room temperature (20 ± 5 °C) for ten months slightly increased its moisture and acidity and decreased its starch content, phenolic content, and pH. Some color changes were observed after 5 months, but sensory characteristics were still acceptable after ten months. Green bananas storage prior to GBF elaboration showed they were suitable for obtaining good quality GBF even after 7 weeks at 6 °C, but only 4 weeks at 12 °C. Discriminant analysis classified the GBF correctly according to the cooperative origin, time, and storage temperature of the bananas used in its preparation. These results provide information that could be used in other banana-producing regions for reducing the environmental impact of fruit waste and obtaining GBF using a simple and inexpensive technological process.