Floral symmetry is a key trait that has played a major role in the diversification of angiosperms, yet the spatiotemporal variations in angiosperm floral symmetry and the drivers of these variations remain poorly explored. A key outstanding question is whether variation in flower symmetry is associated with variation in environmental conditions on geological timescales. Here, using newly compiled data on floral symmetry and global distributions of 259,261 angiosperm species, we mapped global patterns of floral symmetry variation, reconstructed floral symmetry evolution during the Cenozoic and analyzed the impact of climate on the geographical and evolutionary variations of this key trait. We found that the frequency of actinomorphy (radial symmetry) increased with latitude and temperature variability, indicating that species with actinomorphic flowers could better adapt to unstable climates compared with those with zygomorphic flowers (bilateral symmetry). Evolutionary transitions towards zygomorphy dominated floral symmetry evolution, although this transition decreased through the Cenozoic associated with decreasing temperature. Our study provides novel insights into the ecology and evolution of floral symmetry of angiosperms and suggests that climate change may influence species distribution via its effect on floral symmetry.