Background and aims <p>Understanding the drivers of grassland stability under global environmental changes has become a priority for management and policies. Nutrient addition is known to reduce temporal stability of community productivity by altering population stability and species asynchrony, but how these effects vary with nutrient type, level, and duration remains unclear.</p> Methods <p>We conducted a global meta-analysis of 40 studies testing nitrogen (N), phosphorus (P), and combined N + P addition on community stability, population stability and species asynchrony.</p> Results <p>For N addition, the meta-analysis showed consistently negative effects of N on community and population stability (the latter being weaker than community-level) and species asynchrony. These effects intensified with higher N levels but were unaffected by the duration of addition. For P and combined N and P addition, our study demonstrated weak overall effects on stability (at both community and population levels) and species asynchrony, with partially mediated by addition level or duration. Furthermore, the meta-analysis revealed that the effects of nutrient addition on stability and species asynchrony were not influenced by initial species richness, mean annual temperature, or mean annual precipitation—except for a notable negative effect of P addition on species asynchrony in warmer regions.</p> Conclusion <p>Our integrative assessment underscores the importance of considering nutrient-specific and dose-dependent responses when evaluating grassland stability. To promote grassland sustainability, it is crucial to account for the effects of different nutrient types—arising from both managed fertilization and diffuse enrichment sources (e.g., atmospheric deposition and runoff)—as well as the overall levels of nutrient inputs.</p>