The increase in atmospheric CO 2 concentration ([CO 2 ]) due to climate change may alter the composition of communities and the functioning of ecosystems. Owing to greater nitrogen use efficiency, leguminous plants present more effective responses to increasing [CO 2 ] than non-legumes. The objective of this study was to evaluate the morphophysiological and growth responses of two species from the Cerrado, a native C 3 herbaceous legume (Stylosanthes capitata Vogel.) and an invasive C 4 grass (Melinis minutiflora P. Beauv) growing alone or in competition, in ambient (350 ppm) and high (1000 ppm) [CO 2 ]. Competition with S. capitata reduced leaf development and dry matter production in M. minutiflora individuals, regardless of [CO 2 ]. Stylosanthes capitata increased root system growth under high [CO 2 ] and competition. This change allows greater soil exploitation, decreasing nutrient limitation to S. capitata development. The leguminous species S. capitata showed advantages in the competition for resources under high [CO 2 ] concerning the invasive grass. Although invasive C 4 species are initially better in the colonisation of the invaded areas, the C 3 native species of Cerrado may adjust morphophysiological traits when growing at high [CO 2 ] and develop strategies that enable it to more effectively compete for resources.