This study was conducted to investigate the antioxidant and anti-obesity activity of ethanol extracts from fermented Arctium lappa L. Arctium lappa fermented twice with Phellinus linteus (2nd FA) showed more DPPH radical scavenging activity than non-fermented Arctium lappa (NFA), and Arctium lappa fermented once (1st FA) at a concentration of 62.5 ppm. The 2nd FA showed the highest level of ABTS radical scavenging activity at concentration range of 31.5~125 ppm. The ABTS free radical scavenging activities of 1st FA and 2nd FA were similar to that of BHA, a synthetic antioxidant, at a concentration of 250 ppm. The total polyphenol content of 2nd FA was higher than those of NFA and 1st FA. The flavonoid content was significantly increased in 1st FA and 2nd FA than NFA. During adipocyte differentiation, lipid accumulation in 3T3-L1 cells was significantly decreased in the order of NFA, 1st FA, and 2nd FA at all concentrations. In conclusion, the antioxidant and anti-obesity activities of A. lappa were increased depending on the degree of fermentation. It is suggested that fermented Arctium lappa, especially 2nd FA, could be used as a natural ingredient for functional foods and medicine.