Mycorrhizal fungi considerably improve plant nutrition and help them to cope with changing environments. Particularly, these fungi express proteins to transfer inorganic phosphate (Pi) from the soil to colonized roots through symbiotic interfaces. The mechanisms involved in P-i transfer from fungal to plant cells are still largely unknown. Here, we discuss the recent progress made on the description of these mechanisms and we propose the most promising hypotheses and alternative mechanisms for this process. Specifically, we present a phylogenetic survey of candidate P-i transporters of mycorrhizal fungi that might ensure P-i unload into the symbiotic interfaces. Gathering additional knowledge on mycorrhizal P-i transport will improve the P-i-useefficiency in agroecological systems and will guide towards addressing future research challenges.