Cockles(Tegillarca granosa) species that found throughout the Indo-Pacific region and this study was conducted in Yeosu from November 2015 through April 2016. Antioxidant activities (lipid peroxidation, DPPH radical scavenging, superoxide anion radical scavenging, reducing power, and iron chelating assays) were studied at different stages during the processing. The results showed that all cockle samples were related to antioxidant activities, they also possessed effective abilities as free radical scavengers, reducing agents, and iron chelators in most cases. Seasonal variations in antioxidant activities were also observed, characterized by high activity values in April, spring season, a period where phytoplankton is their primary food source which propagates considerably. Moreover, the harvested cockles exhibited the higher radical scavenging activities than marketed cockles by compared in the similar concentration and the activities increased with increasing concentration. The results also showed the useful in the assessment of the cockle potential for the development of functional foods, food ingredients or pharmaceuticals. Moreover, keeping the freshness of the cockle during processing chain is pivotal for keeping its antioxidant activities.