Elevated CO2 concentrations (eCO2) affect plant water relations and carbon (C) sequestration, which may mitigate drought stress. We performed a meta-analysis on the interactive effects of eCO2 and drought on plant ecophysiology. We found a higher leaf relative water content and a less negative midday leaf water potential, resulting from reduced stomatal conductance (gs). However, no soil water-savings were detected due to the counteracting effect of the eCO2-induced increase in leaf area. eCO2 enhanced leaf-level water-use efficiency (WUE) proportionally regardless of soil water regimes. The magnitude of eCO2 enhancement in WUE decreased from leaf to individual scales. There was a stronger A response to eCO2 under drought. eCO2 enhanced biomass production regardless of soil water regimes; especially it enhanced belowground biomass and root to shoot ratio to greater extents under drought. These findings suggest that eCO2 can alleviate the adverse impacts of drought on plant water relations and C sequestration.