This study examined the effects of chestnut powder content (2.5%, 5%, 7.5%, and 10%) on the antioxidant activity and quality characteristics of rice muffins. With the increasing chestnut powder content, the total polyphenol content, flavonoid content, antioxidant activity (determined by radical scavenging activity and reducing power), hardness, gumminess, chewiness, and overall acceptability (determined by sensory evaluation) increased, whereas the moisture content, pH, specific volume, and cooking loss decreased. Regarding color, chestnut powder content was negatively correlated with L and b and positively correlated with a. Notably, overall acceptability abruptly decreased to its minimum at 10%. Thus, adding powder at loadings of <7.5% improved the antioxidant activity and acceptability of rice muffins. Our results can be used as preparatory data for developing a rice muffin model.