A series of 3d–4f binuclear complexes, [M­(3-MeOsaltn)­(MeOH)x(ac)­Ln­(hfac)2] (x = 0 for M = CuII, ZnII; x = 1 for M = CoII, NiII; Ln = GdIII, TbIII, DyIII, LaIII), have been synthesized and characterized, where 3-MeOsaltn, ac, and hfac denote N,N′-bis­(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, acetato, and hexafluoroacetylacetonato, respectively. The X-ray analyses demonstrated that all the complexes have an acetato- and diphenolato-bridged MII–LnIII binuclear structure. The CuII–LnIII and ZnII–LnIII complexes are crystallized in an isomorphous triclinic space group P1̅, where the CuII or ZnII ion has square pyramidal coordination geometry with N2O2 donor atoms of 3-MeOsaltn at the equatorial coordination sites and one oxygen atom of the bridging acetato ion at the axial site. The CoII–LnIII and NiII–LnIII complexes are crystallized in an isomorphous monoclinic space group P21/c, where the CoII or NiII ion at the high-spin state has an octahedral coordination environment with N2O2 donor atoms of 3-MeOsaltn at the equatorial sites, and one oxygen atom of the bridged acetato and a methanol oxygen atom at the two axial sites. Each LnIII ion for all the complexes is coordinated by four oxygen atoms of two phenolato and two methoxy oxygen atoms of “ligand-complex” M­(3-MeOsaltn), four oxygen atoms of two hfac–, and one oxygen atom of the bridging acetato ion; thus, the coordination number is nine. The temperature dependent magnetic susceptibilities from 1.9 to 300 K and the field-dependent magnetization up to 5 T at 1.9 K were measured. Due to the important orbital contributions of the LnIII (TbIII, DyIII) and to a lesser extent the MII (NiII, CoII) components, the magnetic interaction between MII and LnIII ions were investigated by an empirical approach based on a comparison of the magnetic properties of the MII–LnIII, ZnII–LnIII, and MII–LaIII complexes. The differences of χMT and M(H) values for the MII–LnIII, ZnII–LnIII and those for the MII–LaIII complexes, that is, Δ­(T) = (χMT)MLn – (χMT)ZnLn – (χMT)MLa = JMLn(T) and Δ­(H) = MMLn(H) – MZnLn(H) – MMLa(H) = JMLn(H), give the information of 3d–4f magnetic interaction. The magnetic interactions are ferromagnetic if MII = (CuII, NiII, and CoII) and Ln = (GdIII, TbIII, and DyIII). The magnitudes of the ferromagnetic interaction, JMLn(T) and JMLn(H), are in the order CuII–GdIII > CuII–DyIII > CuII–TbIII, while those are in the order of MII–GdIII ≈ MII–TbIII > MII–DyIII for MII = NiII and CoII. Alternating current (ac) susceptibility measurements demonstrated that the NiII–TbIII and CoII–TbIII complexes showed out-of-phase signal with frequency-dependence and the NiII–DyIII and CoII–DyIII complexes showed small frequency-dependence. The energy barrier for the spin flipping was estimated from the Arrhenius plot to be 14.9(6) and 17.0(4) K for the NiII–TbIII and CoII–TbIII complexes, respectively, under a dc bias field of 1000 Oe.