The bidentate 1,3,4-thia-diazole ligand substituted by two 2-pyridyl rings (denoted L) has been found to produce the new monomeric title complex, [Co(C(12)H(8)N(4)S)(2)(H(2)O)(2)](BF(4))(2). The thia-diazole and pyridyl rings surrounding the Co atom are almost coplanar [dihedral angle = 4.35 (7)°]. The mean plane defined by these heterocyclic moieties makes a dihedral angle of 18.72 (6)° with the non-coordinated pyridyl ring. The Co(2+) cation, located at a crystallographic center of symmetry, is bonded to two ligands and two water mol-ecules in a trans configuration in an octa-hedral environment. The tetra-fluorido--borate ions can be regarded as free anions in the crystal lattice. Nevertheless, they are involved in an infinite two-dimensional network along the [010] and [101] directions of O-H⋯F hydrogen bonds.