The title compound was synthesized from the hydrothermal reaction of V₂O₅, H₃PO₄, H₂NCH₂CH₂NH₂ and H₂O in the molar ratio of 0.55∶4∶3.6∶265 at 175 ℃ for 5 d. The structure contains layers built from chains of trans corner-shared [VO₅N] octahedron that are interconnected by [PO₄] tetrahedron. The 2-aminoethylaminium cation is bonded through the nitrogen to the vanadium site as a monodentate ligand. Strong hydrogen bonds hold the layers together. Crystal data: monoclinic, space group P2₁/c (No. 14), a＝0.92108(2) nm, b＝0.72851(1) nm, c＝0.98204(2) nm, β＝101.269(7)°, V＝0.6462(4) nm³, Z＝4, D_c＝2.303 g•cm^－3, R₁＝0.0417, wR₂＝0.0999.

Key words: vanadium phosphate, hydrothermal synthesis, structural characterization