Biodiversity can underpin stability in communities, allowing them to withstand environmental fluctuations without changes in aggregate properties like total abundance or biomass. We investigated the influence of biodiversity on two crucial population-level mechanisms governing abundance stability in mesopredatory coral reef fishes: (i) ’community asynchrony’, where species populations fluctuate inversely over time, and (ii) ’species population stability’, where highly abundant species with significant community contributions display minimal population fluctuations. Analyzing temporal data from 81 reef fish communities across the Indian and Pacific Oceans over a decade, we found that community asynchrony, rather than species population stability, primarily predicts community stability. Functional diversity, not taxonomic diversity, characterised this stability, emphasizing the role of niche differences in stabilizing communities. We highlight that community attributes that promote asynchronous population fluctuations, enhancing response diversity and tempering strong trophic interactions, are vital for stabilizing mesopredatory reef fish communities in the face of global change.