In this study, 1, 3, and 5% of Enteromorpha prolifera (E. prolifera, green laver) powder was added to the rice crispy cereal, a gluten-free food. The quality characteristics and antioxidant activities of rice crispy cereal were investigated. The reducing sugar content decreased with increased contents of E. prolifera powder. In the Hunter color system, the L and a values decreased, while the b values increased with increasing E. prolifera content. The phycocyanin and chlorophyll contents (antioxidant pigments) increased with increasing amounts of E. prolifera. The 5% E. prolifera additive group exhibited the maximum antioxidant and radical (DPPH and hydroxyl) scavenging activities. The flavonoid and total phenolic contents were also the maximum in this group. The intensity test results revealed that rice crispy cereal containing 5% E. prolifera exhibited the highest overall acceptability. Based on these results, The study presents the preliminary data that can be used to improve the nutritional value of rice crispy cereal. The results revealed that powdered E. prolifera can be added in different proportions to various types of food for the development of different food items having varying properties. Key words:Enteromorpha prolifera, rice crispy cereal, quality characteristics, antioxidant activities