$Curcuma$ $caesia$ Roxb. (Zingiberaceae), known as black turmeric in English, is a perennial herb found throughout the Himalayan region, North-East and Central India. The plant has been traditionally used in India for several medicinal purposes. Present study was carried out to evaluate the methanol extract of $C.$ $caesia$ (MECC) rhizome for some $in$ $vitro$ antioxidant studies as because we know that many diseases are associated with reactive oxygen species (ROS) and reactive nitrogen species (RNS). Effect of MECC on ROS and RNS were evaluated in different $in$ $vitro$ methods like 1, 1-diphenyl-2-picrylhydrazil radical, hydroxyl radicals, superoxide anions, nitric oxide, hydrogen peroxide, peroxynitrite and hypochlorous acid. Lipid peroxidation, total phenolic content was also measured by standard assay method. The extract showed significant antioxidant activities in a dose dependent manner. The $IC_{50}$ values for scavenging of free radicals were $94.03{pm}0.67{mu}g/ml$, $155.59{pm}3.03{mu}g/ml$, $68.10{pm}1.24{mu}g/ml$, $21.07{pm}1.78{mu}g/ml$, $260.56{pm}12.65{mu}g/ml$ and $33.33{pm}0.52{mu}g/ml$ for DPPH, nitric oxide, superoxide, hydroxyl, peroxynitrite and hypochlorous acid respectively. Reductive ability of the extract was also tested where dose dependent reducing capability was observed. The rhizome extract contains 677.7 ${mu}g$ of phenolic compound in 10 mg of the extract which is accounted for its free radical as well as antioxidant activity. From the above study it is concluded that the methanol extract of $C.$ $caesia$ rhizome is a potential source of natural antioxidant.