In the title compound, {[Co(C7H7N2O2)2].H2O}n, the CoII atom lies on an inversion centre and has octahedral geometry, defined by two O atoms in axial positions and four N atoms in equatorial sites from six different 3,5-diaminobenzoate ligands. Each 3,5-diaminobenzoate anion acts as a mu3-bridging ligand, linking three adjacent CoII ions through one O atom and two N atoms to form a three-dimensional coordination polymer.