Soybean [Glycine max (L.) Merr.] is an important oilseed crop in central India. Climate change may have a positive or negative impact on crop-weed competition. Hence, an experiment was conducted in open-top chambers (OTC) to study the effect of ambient (A), elevated CO2 (EC), elevated temperature (ET) and elevated CO2+ elevated temperature (EC+ET). EC, ET and EC+ET have a significant encouraging effect on overall growth and yield attributes of weeds and soybean crop. The increase in the biomass of soybean at EC, ET and EC+ET ranged from 21-60% as compared to the ambient conditions. The biomass of Echinochloa colona (10-65%) and Ischaemum rugosum (16-37%) was found to be increased under EC, ET and EC+ET. EC and ET had a positive impact on plant height and leaf area of soybean, E. colona and I. rugosum. The seed yield of soybean was observed to be significantly higher at EC (13%) and EC+ET (46%), however at ET no significant increment over ambient was observed. A higher number of pods and nodules per plant were observed at EC and EC+ET. In the presence of E. colona and I. rugosum, the soybean yield was significantly reduced by 27, 59, 45 and 52% at A, EC, ET and EC+ET conditions, respectively as compared to the weed-free condition. The findings of the present study indicate that C4 weeds may become more competitive with C3 crops, thereby emphasizing the necessity of conducting future studies on C3 and C4 crop-weed competition under changing climatic conditions.