The aim of this study was to investigate the impact of elevated concentration of carbon dioxide (CO₂), as expected over coming decades, on yield and quality of winter bread wheat (Triticum aestivum L.). Plants (cv. Bologna) were grown by using the free-air CO₂ enrichment (FACE) system at Fiorenzuola d’Arda under ambient (control) and elevated (570 ppm, e[CO₂]) CO₂ concentrations for two growing seasons. We addressed whether there would be a response of wheat grains to elevated CO₂ concentration in terms of the contents of nitrogen (N), micro- and macronutrients, proteins and free amino acids. Under e[CO₂], total wheat biomass and grain yield increased in both years of the study. Grain N percentage was reduced under e[CO₂], but grain N yield (kg ha^–1) was increased. Among macro- and micronutrients, a decrease in zinc concentration was observed. The proteome pattern was significantly different in grains grown at the two different CO₂ levels, but the observed changes were highly dependent on interactions with prevailing environmental conditions. Finally, a negative trend was observed in the early germination rates of seeds from plants grown under e[CO₂] compared with the controls. The results suggest that the expected increase in CO₂ levels and their interactive effects with environmental variables may influence agronomic performance by increasing yield and negatively affecting quality.