Free radicals have aroused significant interest among scientist in the past decade. Their broad range of effects in biological systems has drawn on the attention of many experimental works Standardized 50% methanolic leaf extract of Eichornia crassipes were investigated for antioxidant effect. Numerous in vitro methods were used to determine free radical scavenging activity. 50% methanolic leaf extract of Eichornia crassipes were found to cause significant free radical scavenging effects on DPPH, their scavenging potencies as indicated by the decoloration of the solution. The present results underline that the 50% methanolic leaf extract of Eichornia crassipes have antioxidant activity.