The coordinatively unsaturated dinickel(II) complex [(L²)Ni₂](BPh₄)₂ (2), where (L²)²⁻ represents the dianionic form of the 'N₄S₂' ligand N,N′‐bis(2‐thio‐3‐aminomethyl‐5‐tert‐butylbenzyl)propane‐1,3‐diamine), has been investigated with respect to its ability to function as a building block for the preparation of polynuclear nickel complexes with a high‐spin ground state. Treatment of 2 with pyridazine (pydz) followed by addition of two equivalents of NH₄SCN afforded the dinuclear μ‐pyridazine complex [(L²)Ni₂(μ‐pydz)(NCS)₂] (4). The reaction of 2 with pyridazine and NaN₃ in a 1:1:1 molar ratio gave the tetranuclear nickel(II) complex [{(L²)Ni₂(μ‐pydz)(N₃)}₂](BPh₄)₂ (5). Both complexes have been characterized by X‐ray crystallography and variable‐temperature magnetic susceptibility studies. In complex 4 two fac‐(SCN)N₂Ni^II units are linked by two thiophenolate sulfur atoms and a μ‐pydz ligand to give a (SCN)N₂Ni(μ‐S)₂(μ‐pydz)NiN₂(NCS) core structure with a pseudoconfacial bioctahedral geometry. The two NCS⁻ groups occupy opposite coordination sites, each is in a cis position to the pydz bridge. Analyses of the susceptibility data indicate the presence of an intramolecular ferromagnetic exchange interaction between the two Ni^II (S=1) ions. Complex 5 is composed of two binuclear [(L²)Ni₂(μ‐pydz)]²⁺ subunits which are linked by two azide ions to give a rectangular array of four six‐coordinate Ni^II ions. The binuclear [(L²)Ni₂(μ‐pydz)]²⁺ fragments in 4 and 5 are isostructural. Analyses of the susceptibility data of 5 reveal ferromagnetic exchange interactions between the Ni^II ions of the binuclear subunit as well as for the μ_1,3‐N₃‐bridged Ni^II ions. Thus, compound 4 has an S=2 ground state, whereas in 5 it is S=4.