The structure of the title compound, [Ni(ths)(bbip)(dmf)].H(2)O [ths is thiosulfate, S(2)O(3); bbip is 2,6-bis(1H-benzimidazol-2-yl)pyridine, C(21)H(13)N(5); and dmf is dimethylformamide, C(3)H(7)NO], is monomeric, with the nickel ion octahedrally surrounded by an N,N',N"-tridentate bbip molecule, an S,O-bidentate ths molecule and an O-monodentate dmf molecule. The H atoms of the hydration water molecule and the amino groups of bbip are involved in hydrogen bonding and determine a spatial organization of broad layers parallel to (001), which are connected by weak interactions.