The asymmetric unit of the crystal structure of the title complex, [Co(C6H6N2O)(2)(H2O)(4)](C8H5O3)(2)center dot 2H(2)O, contains one-half of the complex cation with the Co-II ion located on an inversion center, a 4-formylbenzoate (FB) counter-anion and an uncoordinated water molecule. The four O atoms in the equatorial plane around the Co-II ion form a slightly distorted square-planar arrangement with an average Co-O bond length of 2.086 angstrom; the slightly distorted octahedral coordination is completed by the two N atoms of the isonicotinamide (INA) ligands at a slightly longer distance [2.1603 (14) angstrom] in the axial positions. The dihedral angle between the carboxylate group and the attached benzene ring is 5.93 (13)degrees, while the pyridine and benzene rings are oriented at a dihedral angle of 3.09 (6)degrees. In the crystal structure, O-H center dot center dot center dot O, N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds link the molecules into a three-dimensional network. pi-pi Contacts between the benzene and pyridine rings [centroid-centroid distance = 3.758 (1) angstrom] may further stabilize the crystal structure.