In title compound, {(C(2)H(10)N(2))(0.5)[In(C(2)O(4))(2)]·2H(2)O}(n), the unique In(III) ion is coordinated by eight O atoms from four oxalate ligands in a distorted square-anti-prismatic environment. The doubly bis-chelating oxalate ligands act as bridging ligands connecting symmetry-related In(III) ions and forming a three-dimensional open framework structure. Ethyl-enediammonium cations and water mol-ecules occupy the voids within the structure. The unique ethyl-enediammonium cation and one water mol-ecule both lie on a twofold rotation axis. One of the other two water mol-ecules residing on general crystallographic sites was refined as disordered with half occupancy. In the crystal structure, cations and water mol-ecules are linked to the anionic framework via inter-molecular O-H⋯O and N-H⋯O hydrogen bonds.