Crystals of the title compound, (C5H8N3)3[VO2(C2O4)2]·2.5H2O, a mononuclear VV complex, were obtained by slow evaporation at room temperature of an aqueous solution containing vanadium pentoxide, oxalic acid and 2,6-diaminopyridine. The asymmetric unit contains one bis(oxalato)dioxovanadate(V) anionic complex, three 2,6-diaminopyridinium cations and two and a half uncoordinated water molecules. The mononuclear vanadium(V) anions are connected to the organic cations and water molecules through a strong N—H...O and O—H...O hydrogen-bond network, consolidated by π–π stacking interactions, to form a three-dimensional structure.