Biscuits were formulated using a 50/50 wheat and purple rice flour mix containing mixed spices, galangal, and defatted green‐lipped mussel powder ( Perna canaliculus ) added in the range of 5–15% of the total biscuit weight. The fortified biscuits had higher protein (26.36%), fiber (52.90%), and ash (6.00%) contents and a lower total fat (5.64%) content compared to the control biscuits. The in vitro starch digestibility and predicted glycemic index (pGI) decreased in the fortified biscuits by 18.95% and 6.18%, respectively, while the in vitro protein digestibility increased by 3.73%, corresponding to the increased levels of defatted mussel powder present. The spread ratio and hardness of the fortified biscuits also increased significantly. The color values of the fortified biscuits after the incorporation of different levels of defatted mussel powder showed significant changes, with a darkening of the biscuit surface and a lowered browning index compared to the control biscuits. Results of the sensory quality evaluation showed that incorporation of defatted mussel powder into the biscuit mix of up to 15% showed no significant differences in liking scores in terms of color, overall appearance; whereas, the flavor and overall acceptability scores were significantly lower than the control biscuits. Overall, defatted mussel powder can be successfully incorporated into biscuit mixes to enrich the protein, fiber, and antioxidant contents of the biscuits.