Although Agaricus bisporus and Pleurotus ostreatus are two major cultivated mushrooms in Iran, a range of different other species of Agaricus and Pleurotus mushrooms grow wild in various habitats of the country. However, limited study has been undertaken to investigate antioxidant potency of the Iranian cultivated or wild mushrooms. This study aimed to evaluate antioxidant capacity of methanol-dichloromethane (1:1) extracts of commercially cultivated and newly cultivated wild species of Agaricus and Pleurotus, using chemical and biochemical techniques. In general, the results revealed that all the tested mushroom demonstrated substantial antioxidant activities against various oxidant systems. Specifically, the newly cultivated wild A. devoniensis proved to be a superior antioxidant among the tested mushrooms, due to having high levels of phenols, efficient scavenging activities on 2,2- diphenyl-1-picrylhydrazyl (DPPH) radicals, relatively high chelating abilities, and an apparent high reducing power. In view of total flavonoids and prevention of lipid peroxidation, however, it was a commercial strain of P. ostreatus that ranked the first. The findings of this research might have implications in preventing oxidative stress-related diseases through the diet; thus they may justify efforts to extract natural antioxidant ingredients from the wild mushrooms tested in this study, or to use them directly in the diet.