Biological properties of the soil have often been proposed as early and sensitive indicators of soil ecological stress or other environmental changes. In the present investigation, the soil samples were collected from weeds associated with rice- wheat cropping system from open- top chambers to assess the effect of elevated CO2 and temperature on soil enzymes. In Rabi season, higher activity of FDA hydrolysis rate was noticed in wild oat with 26.5 (µg fluorescein/g/h) at elevated CO2 + ambient temperature levels. Dehydrogenase activity was higher at enrichment of CO2 for P. minor with 35.9 (µg TPF/g soil/24 h). Urease significantly was higher in enrichment of CO2+ elevated temperature with wild oat 34.6 (µg NH4/g soil/24 h) followed by wheat (31.5µg NH4/g soil/24 h) with elevated CO2 + ambient temperature. In Kharif season, enrichment of CO2 concentration in rhizosphere of Echinochloa crusgalli recorded with higher FDA hydrolysis rate (19.8 µg fluorescein/g/h), dehydrogenase activity (39.8 µg TPF/g soil/24 h) and urease  activity (45.6 µg NH4/g soil/24 h) respectively. We found the carbon dioxide enrichment significantly increased the soil enzymes like dehydrogenase, fluorescein diacetate (FDA) hydrolysis and urease activity in weeds rhizosphere than the crops