Climate change has pronounced impacts on plants, particularly in environments vulnerable to warming such as alpine zones. Although plant responses in tundra and alpine environments from high latitudes have been well-studied at the community level, the overall effect of warming on global alpine plant populations and species remains unclear. We collated global data from 46 open-top chamber (OTC) studies conducted on alpine plants from mountain belts worldwide and assessed potential effects of warming on plant performance. In addition, we examined warming responses of plants from the tundra zone (Arctic tundra and alpine tundra) in circumpolar regions. In terms of growth and reproductive output, the overall response of 91 plant species was highly positive. Shrubs grew significantly larger and expressed higher reproduction under warming compared to forbs and graminoids. Arctic tundra plants tended to respond more positively to warming compared to alpine tundra plants. We also found that plant responses were greater with increasing precipitation across circumpolar tundra, but not across alpine zones. Phenotypic plasticity in size- and fitness-related traits were similar for both alpine and tundra zones. Our findings support the notion that global warming can cause significant changes to alpine environments. Due to changes in biotic interactions, alpine tundra plants may be more negatively affected by warming compared to Arctic tundra plants which responded more positively to warming. Similarly, if shrubs are most advantaged under warming, their invasion into higher elevations may threaten the ecological functioning of alpine ecosystems, which is another serious challenge from climate change.