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Predator satiation is the most commonly tested hypothesis that explains the evolutionary advantages of masting. It proposes that masting benefits plant reproduction by reducing the proportion of seed crop that is consumed by predators. This hypothesis is widely accepted, but many theoretical notions about predator satiation have not been subjected to a robust evaluation. To address this issue, we conducted a meta-analysis of studies that quantified seed predation in relation to mast seeding. We found evidence of both numerical (starvation between mast years) and functional (satiation during mast years) response of consumers to masting. These two effects reinforced each other. Masting satiated invertebrate but not vertebrate seed predators. Satiation was more pronounced at higher, temperate, and boreal latitudes, perhaps because masting is more effective in reducing seed losses when plant communities are less diverse. The effectiveness of masting in satiating invertebrate consumers declined over time (1972 to 2018), probably reflecting the impact of climate change on the frequency and intensity of masting. If masting ceases to reduce seed losses, a crucial advantage of this reproductive strategy will be lost, and sustainability of many tree populations will decline. [ABSTRACT FROM AUTHOR]