Mycorrhizal symbioses are prevalent in terrestrial ecosystems and play essential roles in plant nutrition and health. However, the relative importance of plant evolutionary history, physiology, and eco-geographical factors in shaping mycorrhizal fungal community assembly remains poorly understood. Here, we investigate how plant phylogeny, trophic mode, biogeographic distribution and environmental niche collectively influence the diversity and composition of mycorrhizal fungal communities across the Orchidaceae, spanning broad phylogenetic and ecological scales. By using family-wide orchid-fungal associations and global occurrence data, our analyses showed that the variation in fungal diversity and community structure can be partially explained by orchids’ trophic mode, biogeographic distribution and environmental niche, but not by their overall phylogenetic relatedness. Among trophic modes, partially mycoheterotrophic orchids exhibited the highest level of fungal diversity (the lowest level of fungal specificity) in association with a broad range of phylogenetically dispersed fungal partners. Between biogeographical regions, a significantly higher level of fungal specificity was found for orchid species distributed in Australia than those in Eurasia and Africa. Furthermore, multivariate analyses showed that a small portion of the variation in fungal community structure was significantly related to broad climate, soil and vegetation variables, indicating the existence of large-scale habitat filtering on orchid mycorrhizal communities. Altogether, our findings indicate that mycorrhizal communities in the orchid family are likely shaped by multiple, intertwined factors related to orchid ecophysiology and biogeography on a global scale.