Common mycorrhizal networks of arbuscular mycorrhizal fungi have been reported to transfer cesium between plants. However, a direct hyphae-mediated transfer (via cytoplasm/protoplasm) cannot be distinguished from an indirect transfer. Indeed, cesium released by the roots of the donor plant can be taken up by the receiver plant or fungal hyphae. In the present study, Medicago truncatula plants were connected by a common mycorrhizal network and Prussian Blue (ammonium-ferric-hexacyano ferrate) was added in the growth medium to adsorb the released radiocesium. A direct transfer of radiocesium to roots and shoots of the receiver plant was clearly demonstrated for the first time. Even though this transfer was quantitatively low, it suggested that shared mycorrhizal networks could contribute to the redistribution of this radionuclide in the environment, which otherwise would be restricted both in time and space. This finding may also help to understand the behaviour of its chemical analogue, potassium.