Oxidative stress is strongly implicated in aging and in the progression of diseases. Antioxidants, especially of natural origin, are valued for their protective as well as curative health benefits. Numerous mushroom species have shown marked antioxidant effect. This can prove beneficial when mushrooms are used as nutraceuticals or for drug development. In the current investigation the antioxidant potential of some medicinal mushrooms, namely Inonotus pachyphloeus, Phellinus allardii, Ph. fastuosus, Ph. sanfordii and Ph. torulosus was examined employing different assays. The ethanol extracts of the fruiting bodies of these mushrooms were evaluated in vitro for scavenging potential against DPPH, hydroxyl radicals, superoxide radicals, as well as the reducing power. The free radical scavenging activity of mushroom extracts followed the trend of Ph. fastuosus > Ph. sanfordii > Inonotus pachyphloeus > Ph. torulosus > Ph. allardii. Ph. fastuosus and Ph. sanfordii extracts exhibited significant DPPH and superoxide radical scavenging activities, statistically (P < 0.05) comparable to each other and to the standard catechin. Ph. fastuosus extract (EC50 = 16 ± 1.15 μg/mL) showed the most significant hydroxyl radical scavenging activity even higher than the standard. In reducing power assay, Ph. torulosus extract (EC50 = 320 ± 0.02 μg/mL) exhibited the most significant reducing power statistically (P < 0.05) comparable with the reduced form of glutathione. The tested mushroom extracts were found to consist of appreciable amounts of carbohydrates, phenols and proteins. The free radical scavenging efficacy of the examined mushrooms showed positive correlation with their phenol content. These medicinal mushrooms are good natural antioxidants and can be incorporated in nutraceuticals/pharmaceuticals after detailed studies.