The industrial revolution, population explosion, urbanization, and the use of advanced technological instruments have accelerated the consumption of fossil fuels leading to changes in the gaseous composition of the Earth’s atmosphere. The combustion of fossil fuel acts as a principal source of carbon dioxide (CO2) and is still contributing to its continuous rise in the atmosphere. The levels of CO2 in the atmosphere have significantly increased since the preindustrial era and future projections predict that its concentration will be doubled in the next 50 years, which will cause a significant impact on global weather patterns, including temperature increases by an average of 0.5°C per decade. As per future projections regarding greenhouse gases made by the Intergovernmental Panel on Climate Change, the projected levels of CO2 will range from 500 to 1000 ppm by the end of the 21st century. Currently, crop plants are exposed to CO2 levels that have not been experienced from the time of the preindustrial era, and agriculture is facing a future of uncertain consequences of global climate change. An understanding of the influence of climate change on future crop production requires an appreciation of the general responses of a range of crop types to elevated CO2 contents and the ways in which those affects interact with other factors. Rising CO2 is considered an important aspect of global climate change as it has the potential to enhance crop productivity, which will be required to feed the increasing population across the globe. The objective of this chapter is to present an overview of the responses of plants to high CO2 and the fundamental mechanisms behind those responses. © 2019 Elsevier Inc. All rights reserved.