We applied a diversity partitioning approach to identify the influence of multiple environmental factors on taxonomic, functional and phylogenetic diversity of estuarine fish assemblages at different spatial scales. Our aim was to determine (1) how variation in γ-diversity (estuary scale) is supported by changes in α- (local scale) and β-components (dissimilarity between these two scales) for the three diversity facets and (2) how these diversity measures are related to biogeographic, hydroclimatic, marine, estuarine and land cover conditions. Fish assemblages were sampled using standardized beam trawl surveys in 32 estuaries during spring and autumn (period 2005