Radical scavenging activities of Asterina pectinifera fermented with Cordyceps militaris mycelia. Asterina pectinifera was fermented with Cordyceps militaris mycelia for improvement of anti-oxidant activities. DPPH, alkyl, hydroxyl, and superoxide radical scavenging activities were evaluated using electron spin resonance. Anti-oxidant activities were also determined based on the ferric reducing anti-oxidant power assays and the ABTS radical scavenging activity. The lipid peroxidation inhibition activity was confirmed using ferric thiocyanate and thiobarbituric acid assays. The free radical scavenging activity and anti-oxidative effects of A. pectinifera fermented with C. militaris mycelia (FACM) extracts were higher than for A. pectinifera and C. militaris mycelia extracts alone. FACM extracts contained different biochemical ingredients due to fermentation of A. pectinifera and provide a beneficial anti-oxidant activity. FACM extracts are a promising source of beneficial antioxidants for use in food industries.