Symbioses with mycorrhizal fungi and nitrogen-fixing bacteria (NFB) enhance nitrogen (N) acquisition in host plants and maypromote N transfer to neighbouring plants through mycorrhizal networks (MN). Nevertheless, the extent and mechanisms ofthis transfer remain unclear. On the basis of a synthesis of 15 N labeling studies, we show that MN and NFB synergistically en-hanced interplant N sharing. In the presence of MN, N transfer from N-fixing donors to non-N-fixing receivers increased by anaverage of 9.7-fold, accounting for 5.61% of the total N in receiver plants. Moreover, greater amounts of N were transferred fromN-fixing plants towards their phylogenetically distant plants. Source-sink gradients driven by differences in N content betweenneighbouring plants further promoted N transfer. Together, our findings highlight the ecological significance of an expandedMN framework in explaining interplant N sharing and provide new insights into how symbiotic guild interactions promote spe-cies coexistence and biodiversity maintenance.