The article describes syntheses, crystal structures and magnetic properties of six defective dicubane type NiII4 clusters of compositions [NiII4(HL1)2(µ3‐X)2(µ1,1‐N3)2(µ1,3‐carboxylato)2]·nH2O (1, X = OMe–, carboxylato = o‐benzoylbenzoato, n = 0; 2, X = {(OMe–)0.83(N3–)0.17}, carboxylato = phenyl acetato, n = 2; 3, X = {(OMe–)0.80(N3–)0.20}, carboxylato = salicylato, n = 0; 4, X = OH–, carboxylato = o‐benzoylbenzoato, n = 2; 5, X = {(N3–)0.58(OMe–)0.42}, carboxylato = o‐benzoylbenzoato, n = 2) and [NiII4(HL1)2(µ1,1,1‐N3)2(µ1,1‐N3)2(N3)2(H2O)2]·4DMF (6), where H2L1 is 2‐Formyl‐6‐{(2‐hydroxy‐1,1‐dimethyl‐ethylimino)‐methyl}‐4‐ethyl‐phenol, and this is the partially hydrolyzed product of initially employed ligand H3L, 2,6‐bis‐{(2‐hydroxy‐1,1‐dimethyl‐ethylimino)‐methyl}‐4‐ethyl‐phenol. Each of the two compartments of each [HL1]– in 1–6 is occupied by a NiII ion, to form a NiII2 fragment. The common bridges between the two metal ions in a dinuclear fragment are µ‐phenoxo of [HL1]– and one µ3‐core ligand (methoxo/hydroxo/mixture of methoxo and µ1,1,1‐azido) while the additional bridge in 1–5 is a µ1,3‐carboxylato. Two dinuclear fragments are interlinked by two µ1,1‐azido and two µ3‐core ligands. Interestingly, the µ3‐methoxo compound 1 and the µ3‐hydroxo compound 4 are interconvertible in both ways as the function of the solvents. Variable‐temperature and variable‐field magnetic studies reveal overall ferromagnetic interactions in each of 1–6.