Incorporating dried corn silk powder (CSP) into food products is considered beneficial for health and suitable for individuals of all ages. Thus, our study is designed to evaluate the effects of adding CSP to prepared cookies as a nontraditional source of dietary fiber and natural antioxidants, focusing on the chemical composition, physical properties, color attributes, antioxidant activity, and sensory properties of fortified cookies. Different CSP proportions (5%, 10%, 15%, and 20%) replaced wheat flour (WF) with a 72% extraction rate. The results revealed that CSP had significant levels of total phenolic content (TPC) and flavonoid content (TFC), measuring 86.42 mg GAE/g and 112.68 mg QE/g, respectively. CSP contained higher quantities of protein and fiber than WF, with values of 14.81 g and 15.21 g per 100 g of flour weight basis, respectively. The amounts of phenolic compounds in cookie samples increased proportionally with the increasing substitution of CSP, while total carbohydrates decreased. Adding CSP at concentrations of 5%, 10%, 15%, and 20% resulted in corresponding increases in crude fiber of 0.52, 1.2, 2.04, and 2.7 times compared to the control cookie samples. As the amount of CSP supplementation increased (0–20%), TPC and TFC in the cookies increased to 3.06 and 4.08 mg GAE/g and 0.02 to 1.28 mg QE/g, respectively. Increasing CSP proportions led to a significant decrease in diameter, thickness, spread factor, volume, and density of fortified cookies. Furthermore, the L* value exhibited a substantial decline from 65.48 to 51.12 as the amount of CSP substitution increased from 5% to 20%. The sensory evaluation characteristics of the cookie samples indicated that the sample with 15% CSP had the highest overall acceptability score. Therefore, this study demonstrates that adding 15% CSP can effectively yield functional cookies without compromising their sensory acceptability.