Trees within farmers' fields can enhance systems' longer-term productivity e.g., via nutrient amelioration, which is indispensable to attain sustainable agroecosystems. While arbuscular mycorrhizal fungi (AMF) are known to improve plant access to soil nutrients, the potential of AMF to facilitate nutrient transfer from trees to crops is unclear. We used the 15N (nitrogen) natural abundance technique together with root and AMF exclusion plots to assess if Faidherbia albida (faidherbia) trees deliver N to maize via associated AMF in smallholder fields. We show, here, that within one cropping season, maize obtained approximately 35 kg biologically fixed N ha-1 from faidherbia and AMF significantly contribute to this transfer of N. One third of tree-derived N in maize leaves was attributed to transfer via AMF and two thirds were explained by tree leaf litter input. Thus, the faidherbia-AMF association can enhance agroecosystem functioning and as such, attain greater sustainability of low-input cropping systems.