Antioxidant activity of four mushrooms was assayed by using 2,2-diphenyl-1-picrylhydrazyl (DPPH), reducing power, iron chelation, ABTS, DPPH and hydroxyl radical. Furthermore, total phenol and flavonoid contents of these mushrooms extract were also determined. Rutin and quercertin were used as standards. All the four mushrooms exhibited potent and concentration dependent free radical scavenging activity in all the assays tested. However, Pleurotus ostreatus had the highest radical scavenging ability. Reductive ability of these mushrooms were also found to increase with increase in concentration. Total phenol and flavonoid content determination showed that all the mushrooms are rich in phenols and flavonoids. Pleurotus ostreatus had the highest phenolic and flavonoid content among the four mushrooms indicating that it has the highest antioxidant capacity among the mushrooms studied. All the results of the in vitro antioxidant assays reveal potent antioxidant and free radical scavenging activity of P. eryngii, T. robustus, P. cinnabarinus, P. ostreatus. This potent antioxidant activity may be attributed to its high phenolic and flavonoid contents and may be responsible for their nutritional and therapeutic uses.