In the title compound, [Cu(C5H3N2O2)2(H2O)2], the Cu(II) ion, located on an inversion center, exhibits an octa-hedral coordination geometry. The equatorial plane is defined by two trans-related N,O-bidentate pyridazine-3-carboxyl-ate ligands and the axial positions are occupied by two water mol-ecules. In the crystal, mol-ecules are connected by O-H⋯O hydrogen bonds between the water mol-ecules and the noncoordinating carboxyl-ate O atoms, forming layers parallel to the bc plane. The layers are stacked along the a axis by further O-H⋯O hydrogen bonds between the water mol-ecules and the coordinating carboxyl-ate O atoms. Weak C-H⋯O hydrogen bonds are also observed between the pyridazine rings and the water mol-ecules and between the pyridazine rings and the non-coordinating carboxyl-ate O atoms.