In the crystal structure of the title compound, {[Co(C 11 H 9 NSO 5 )(C 10 H 9 N 3 )]0.5C 3 H 7 NO·H 2 O} n or {[Co(dmtb)(dpa)]·0.5DMF·H 2 O} n (dmtb 2- = 5-[(di-meth-yl-amino)-thioxometh-oxy]-1,3-benzene-dicarboxyl-ate and dpa = 4,4'-di-pyridyl-amine), an assembly of periodic [Co(C 11 H 9 NSO 5 )(C 10 H 9 N 3 )] n layers extending parallel to the bc plane is present. Each layer is constituted by distorted [CoO 4 N 2 ] octa-hedra, which are connected through the μ 2 -coordination modes of both dmtb 2- and dpa ligands. Occupationally disordered water and di-meth-yl-formamide (DMF) solvent mol-ecules are located in the voids of the network to which they are connected through hydrogen-bonding inter-actions.