The crystal and molecular structures of three new nickel complexes are presented: diaqua (4,4´-dimethylbipyridine- N,N´)(methanol) thiosulfato(S) nickel(II) (1), aqua terpyridine(N,N´,N´´) thiosulfato(S,O) nickel(II) hemihydrate (2) and bis(dipyridylamine) thiosulfato(S,O) nickel(II) hemihydrate (3). Compound (1) is triclinic, P 1^-, a 8.1570(16), b 9.6847(19), c 11.714(2) Å, α 76.73(3), β 73.56(3), γ 78.23(3)°, V854.2(3) ų, Z 2, conventional R (onF) being 0.034 for 5515 N_o observed reflections (I > 2σ(I)). Compound (2) is monoclinic,C2/c, a 27.866(6), b 9.2743(19), c 14.216(3) Å, β 114.24(3)°, V 3350.1(12) ų, Z 8, R 0.034, N_o 5690. Compound (3) is orthorhombic, Iba2,a 12.9860(10), b 16.8210(10), c 19.4790(10) Å, V 4254.9(5) ų, Z 8, R 0.038, N_o 3956. The three compounds are monomeric, with the nickel ion in a distorted octahedral coordination. In compound (1) the thiosulfate anion binds through sulfur as a monodentate ligand, while in the other two it behaves as a chelate, binding through oxygen and sulfur. The strong hydrogen-bonding interactions involving the aqua ligands and the water solvate molecules define chains with a strong internal connectivity and which are loosely linked to each other via much softer C–H⋯O interactions.