Posidonia oceanica seagrass is facing multiple stressors that can alter ecosystem functioning and plant traits. Among these, leaf bleaching, a senescence-related depigmentation process, has been observed in some areas of the Mediterranean Sea. Bleaching was related to processes that lead to a low structural investment, but the main drivers that distinguish it from brown necrosis remain unclear. This study aimed to identify the environmental factors influencing leaf bleaching across the Mediterranean Sea through a correlative and mensurative approach. In summer 2025, over 70 researchers collected 419 observations on the presence/absence of bleached meadows, while environmental variables were obtained from Copernicus Marine datasets. Morphological and structural data, including leaf area, brown necrotic and bleached area, and leaf mass per area (LMA), were collected from shoots in 32 sites. CLM used to correlate environmental satellite data to bleaching occurrence, indicated that higher depth, chlorophyll-a concentrations and salinity were associated with reduced bleaching incidence, while high temperature and nitrate concentrations increased bleaching. The interaction between nitrates and temperature suggested a weakening of nitrate effects under warmer conditions, highlighting complex stressor interactions. GLMMs, used to correlate bleached leaf area to structural and morphological variables, showed that bleaching decreased with higher LMA, indicating that leaves with greater structural investment are less susceptible. Spatial variability among sites explained a substantial proportion of the observed variance. In contrast, brown necrosis did not show significant relationships with the explanatory variables, suggesting different underlying mechanisms from bleaching. Overall, leaf bleaching was more frequent in shallow meadows and under stressful environmental conditions such as low salinity, eutrophication, and high temperature, and was associated with structurally weaker leaves. Leaf bleaching may affect plant resilience to multiple stressors and understanding both individual and interactive environmental drivers for the conservation and management of this key Mediterranean species become pivotal.