Banana peels are industrial waste that is normally being utilized for biogas production or disposed of without use. By converting banana peels into flour, the waste product can be reduced and the benefits that originate from its fibre and bioactive substances can enhance the nutritional value in other food products. Furthermore, the flour will increase the economical source of the industry as it is obtainable at a low-cost. The transformation of banana peels (waste) into flour (food ingredient) can improve the sustainability of the food chain and promote consumers' health. The unripe banana peel flour (UBPF) constitute of 41.4% total starch and 37.6% total dietary fibre with a higher percentage of insoluble dietary fibre than soluble dietary fibre. Various levels of UBPF from Berangan variety ranging from 0% to 40% were incorporated in the formulation of biscuits. The partial substitution of UBPF significantly increased the total dietary fibre content of biscuits from 1.83% to 4.70%. Starch hydrolysis and estimated glycemic index (eGI) of biscuits were analysed by enzymatic in-vitro digestion. The result showed that partial substitution of Berangan BPF significantly decreased (p<0.05) the starch digestion rate thus lowering the eGI of biscuits from high eGI food to intermediate GI food. UBPF has great potential as a functional ingredient to improve the nutritive value of foods as well as to reduce the glycemic index of food products.