Introduction: The outer brown layer of the coconut kernel is called “Testa”, a byproduct of the coconut processing industry. After the oil extraction process, it can be converted into fine flour, which is a nutritious flour for food formulation. Therefore, this research aims at developing a nutritional flat bread with defatted coconut testa flour and performing its quality evaluation. Method: The testa flour (T1;0%, T2;20%) was substituted with wheat flour to make a selected composite flour for coconut flatbread preparation. Then, the composite flour (50%) of each treatment was mixed with grated coconut (33%), water (15%), and salt (2%). The dry ingredients were mixed first, followed by the addition of water to make a consistent dough. The dough was flattened with uniform thickness (15 cm diameter and 5 mm thickness) and baked on a pan for 3 minutes on each side. Results: The crude fibre content (7.04 ± 1.15%), total phenolic content (3.05 galic acid equivalent mg/g), and scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH;5mM) (69.88%) of the T2 treatment were significantly (p<0.05) higher than those of T1 (1.80 ± 0.16%, 0.92 galic acid equivalent mg/g, and 40.67% respectively). Significantly higher mineral content of Fe (47.83 mg/kg), Mg (1364 mg/kg), and K (3841 mg/Kg) was observed in the T2 treatment compared to T1 (12.94 mg/Kg, 743.33mg/Kg, and 1800mg/Kg, respectively). In the glycemic index analysis, however, healthy subjects confirmed that testa flour (Glycemic Index: 28.32) incorporation has the potential to reduce blood glucose concentration compared to the T1 treatment (Glycemic Index: 35.47). Conclusions: The researchers concluded that the incorporation of defatted testa flour into the coconut flatbread improves the nutritional and glycemic-lowering potential.