Rising atmospheric carbon dioxide concentration (CO₂) and temperature are likely to influence pathways of photosynthesis, growth and yield. The objective of this research was to study the effects of elevated CO₂ and high temperature on leaf gas exchange, activities of Rubisco and PEPC, and growth of grain sorghum (Sorghum bicolor L. Moench cv DeKalb 28E). Plants were grown in sunlit controlled-environment growth chambers at diurnal daytime maximum/nighttime minimum temperatures of 30/20 or 36/26°C at either ambient (350 µmol mol^-1) or elevated (700 µmol mol^-1) CO₂. Gas exchange rates, activities of Rubisco and PEPC, leaf area and component (leaf, stem and total) dry weights were measured at different stages of leaf ontogeny and plant growth. At 6-25 days after leaf tip emergence (DALE), leaf carbon exchange rate (CER) at elevated CO₂ was 20-23% greater at 30/20°C and 10-24% greater at 36/26°C. Elevated CO2 decreased stomatal conductance across all stages of leaf ontogeny by about 17%, while transpiration rates were decreased only at 30/20°C at 6 and 12 DALE. The positive response of CER to elevated CO₂ was greater in young leaves compared to old leaves. In young leaves (6 and 12 DALE), elevated CO₂ enhanced Rubisco activity by 22 and 23% at 30/20°C, and by 17 and 74% at 36/26°C. PEPC activity was not affected by elevated CO₂ at 30/20°C, but was enhanced by 13% at 36/26°C at 6 DALE. At 30/20°C, growth (leaf, stem and total plant dry weight) was increased at elevated CO₂ by 32-49% only at 50 days after sowing (DAS). At 36/26°C growth was progressively enhanced by elevated CO₂ at all stages of plant growth, and was 49-62% higher at 50 DAS. Thus, for C₄ grain sorghum there was an enhancement in CER and Rubisco by elevated CO₂ and temperature at early stages of leaf ontogeny.