Chlorella is an attractive potential food source because it is high in protein and other essential nutrients; when dried, it is about 45% protein, 20% fat, 20% carbohydrate, 5% fibre, and 10% minerals and vitamins. It has been widely used as a well-being food. We investigated the quality characteristics of cookies prepared after addition of various concentrations of chlorella powder (0%, 1%, 3%, and 5%, all w/w) as a substitute for flour. In this study, as chlorella powder concentration rose, decreases in the moisture content, pH, L, a and b value became evident. The spread factor and hardness of the cookies slightly increased after the addition of chlorella powder. Sensory evaluation scores in terms of color, flavor, and texture were statistically very similar, but taste and overall acceptability scores were lower than those of the control. The result of this study showed that the quality of the cookies with the addition of 1% chlorella powder was the best in terms of its taste, flavor, texture, and sensory properties.