Stomata control the flow of gases between plants and the atmosphere. This review is centered on stomatal responses to elevated CO₂ concentration and considers other key environmental factors and underlying mechanisms at multiple levels. First, an outline of general responses in stomatal conductance under elevated CO₂ is presented. Second, stomatal density response, its development, and the trade-off with leaf growth under elevated CO₂ conditions are depicted. Third, the molecular mechanism regulating guard cell movement at elevated CO₂ is suggested. Finally, the interactive effects of elevated CO₂ with other factors critical to stomatal behavior are reviewed. It may be useful to better understand how stomata respond to elevated CO₂ levels while considering other key environmental factors and mechanisms, including molecular mechanism, biochemical processes, and ecophysiological regulation. This understanding may provide profound new insights into how plants cope with climate change.