Increasing atmospheric CO2 concentration (CO2)has led to concerns about global environmental changes including potential increases in global temperatures. The impacts of CO2 with changes in temperature on C4 crops like sorghum are not clearly understood. The objectives of this study were to determine the effects of season-long exposures to treatments of [CO2] (360 and 720 mmol mol-1), and temperatures (20/12, 30/22, 35/27 and 40/32 °C) on growth, biomass accumulation and partitioning of sorghum in eight sunlit, controlled environment chambers under optimum water and nutrient conditions. Plant height and leaf number were recoded weekly on nine plants. Dates of panicle initiation and flowering were also recoded on nine plants. There were no significant CO2 effects on plant height, leaf numbers, time to flowering and weights of various plant components, while significant temperature effects were observed for the all these parameters. Results clearly show that elevated CO2 levels could not compensate the damaging effects caused high temperatures on growth, biomass and partitioning. Cardinal temperatures were calculated for all the parameters studied. The Tmax for above ground biomass was 42.7 °C at ambient CO2 conditions and 47.5 °C for elevated CO2 conditions, while Topt and Tmin did not differ much with CO2 treatments and ranged from 27.3 to 29.9 °C (Topt) and 11.9 to 12.3 °C (Tmin). The high Tmax observed for the vegetative biomass was not reflected for reproductive biomass, i.e. even though plants produced enough vegetative biomass at higher temperature treatments, the plants could not produce any panicles. The Topt and Tmax for reproductive biomass averaged over CO2 treatments were 25.9 and 35.7 °C, respectively. Therefore, under future environments where sorghum is grown under well-watered conditions, increasing CO2 concentrations may not ameliorate the deleterious effects of high temperatures on reproductive process.