The reactions of M(OAc)2·4H2O (M = Ni, Co) with three unsymmetrical amine‐diol ligands RN(CH2CH2OH)(CH2CH2CH2OH) (H2Ln: n = 1, R = benzyl; n = 2, R = 4‐methylbenzyl; n = 3, R = 2‐naphthalenylmethyl) in the presence of NEt3 or pyridine in MeOH or BnOH gave the tetranuclear complexes [M4(HLn)2(OAc)6(MeOH)2] {M = Ni, n = 1 (1a), 2 (1b), 3 (1c); M = Co, n = 1 (4a), 2 (4b), 3 (4c)} and [M4(HLn)2(OAc)6(BnOH)2] {M = Ni, n = 1 (2a), 2 (2b), 3 (2c); M = Co, n = 1 (5a), 2 (5b), 3 (5c)}. When p‐xylene‐α,α′‐diol was used instead of monoalcohols, the tetranuclear {M4O6} units were linked by p‐xylene‐α,α′‐diol to form the 1D coordination polymers [M4(HLn)2(OAc)6(p‐HOCH2C6H4CH2OH)]m {M = Ni, n = 1 (3a), 2 (3b); M = Co, n = 1 (6a), 2 (6b)}. The structures of 1–6 were determined by X‐ray crystallography and consist of centrosymmetrical tetranuclear {M4O6} face‐shared defective double‐cubane cores supported by two monodeprotonated (HLn)– ligands. The mixed‐metal tetranuclear complexes [Ni2.2Co1.8(HL1)2(OAc)6(MeOH)2] (7) and [Mn1.7Ni2.3(HL1)2(OAc)5(OMe)2] (8) were also synthesized by using equimolar amounts of Ni2+ and M2+ (M = Co, Mn) ions. X‐ray crystallographic and fluorescent analyses revealed that 7 is isomorphous with 1a and 4a and contains nonstoichiometric amounts of disordered Ni2+ and Co2+ ions in an average ratio of 2.2:1.8 with different occupancies for the two crystallographically independent metal centers. In contrast, 8 consists of a C2‐symmetrical face‐shared defective double‐cubane {MII3MnIIIO6} core with a Ni/Mn ratio of 2.3:1.7; the amounts of Ni2+ and Mn2+ ions vary depending on the metal sites, and one of the C2 axial positions is exclusively occupied by Mn3+ ions. Detailed magnetostructural analyses on the nickel (1a, 2a, 3a) and cobalt (4a) complexes with appropriate spin‐Hamiltonian models showed that both ferro‐ and antiferromagnetic spin exchange interactions were involved within the tetranuclear units, and their extent depends on the combination of the metal ions and the ligand systems in a delicate fashion.