The title compound, {(C(2)H(10)N(2))[Tl(2)(C(10)H(2)O(8))(H(2)O)(2))]}(n), was prepared using (enH(2))(2)(btc)·2H(2)O and thallium(I) nitrate (en = ethyl-enediamine and btcH(4) = benzene-1,2,4,5-tetra-carboxylic acid). The enH(2) cation and btc ligand are each located on an inversion centre. The Tl(I) atom is seven-coordinated by three btc ligands and two water mol-ecules in an irregular geometry due to the stereochemically active lone pair on the Tl centre. The water mol-ecule and btc ligand are bonded to the Tl atoms in μ- and μ(6)-forms, respectively, leading to a three-dimensional structure. The crystal structure involves O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, and also a Tl⋯π inter-action of 3.537 (1) Å.