Stomata play a pivotal role in regulating gas exchange between terrestrial plants and the atmosphere controlling water and carbon cycles at organismal, ecosystem and global levels. Accordingly, our objective was to investigate the impact of ultraviolet-B radiation, a neglected environmental factor varying with ongoing global change, on stomatal morphology and function by means of a comprehensive meta-analysis. We found 45 peer-reviewed publications containing altogether 143 case studies for analysis. The overall UV effect at the leaf level is to decrease stomatal conductance, stomatal aperture and stomatal size, although stomatal density was increased. The significant decline in conductance is marked in short-term experiments, with more modest decreases noted in long-term UV studies. We found that short-term experiments in growth chambers are not representative of long-term field UV effects on stomatal conductance. Further, we found a stronger UV effect in grasses than in herbs, while the reduction of stomatal conductance was insignificant in trees. It is hypothesised that these alterations in stomatal function have important potential consequences for plant life. In the short term, UV-mediated stomatal closure may reduce transpiration and alleviate drought stress. However, in the long term more complex changes in stomatal aperture, size and density may reduce carbon sink capacity, and enhance leaf and surface warming, potentially exacerbating the negative effects of drought and/or heatwaves on plant ecosystems and endangering long-term plant survival.