The preparation and investigation of multinuclear heterometallic 3d-4f complexes have attracted considarable interest due to their potentional application in information storage and processing, and molecular spintronics. A new trimetallic hexanuclear [FeIII3MnIIIDyIII2(OH)2(is)6(N3)2(bdea)4]•2(MeOH) (1) cluster (His = isobutyric acid, H2bdea = butyldiethanolamine) has been prepared by the reaction of μ3-oxo trinuclear [Fe3O(is)6(H2O)3](NO3)·2(H2O)∙2(MeCN) precursor with Dy(NO3)3∙6H2O, Mn(is)2, sodium azide, and butyldiethanolamine in methanol solution. Single-crystal X-ray diffraction measurements revealed that 1 crystallizes in the orthorhombic space group Pbca, a= 16.9814(1), b= 26.5497(2), c= 35.4422(3) Å. The metal core of 1 is composed of three FeIII atoms, one MnIII atom, and two DyIII atoms bridged by two µ3-OH groups, four isobutyrates and two butyldiethanolamine ligands (Fig. 1). Two azide ligands complete the coordination surrounding of two transition metals, while two monodentate isobutyrates fulfil the coordination spheres of Dy atoms. Transition metal atoms are six-coordinated and have a distorted octahedral geometry. Two of them have a N2O4 donor atom environment, which comprises a N atom from an azide, and a N atom of bdea²- ligand (M-Nazide, 2.007(1) – 2.075(6) Å; M-Nbdea, 2.0225(9) – 2.228(7) Å), an O atom from carboxylate, and three O atoms of two bdea2- ligands (M-Ocarb, 1.974(1) Å; M-Obdea, 1.929(1) – 2.163(1) Å). Two others have a NO5 coordination environment, which comprises a N atom of bdea2- (M-Nbdea, 2.244(1) – 2.245(6) Å), three O atoms of two bdea2- ligands, an O atom of isobutyrate and an O atom of hydroxyl group (M-Obdea, 1.971(1) – 2.069(1) Å; M-Ocarb, 1.974(1) Å; M-OOH, 1.948(1) Å). The Dy atoms have an O8 donor set resulting in a distorted square antiprism polyhedron by three O atoms from carboxylate, three O atoms of three bdea2- ligands, and two O atoms of hydroxy groups (Dy-Ocarb, 2.300(1) - 2.361(1) Å; Dy-Obdea, 2.300(1) – 2.528(1) Å; Dy-OOH, 2.375(1) – 2.430(1) Å).  he position of monodentate isobutyrate ligands is stabilized by O-H∙∙∙O intramolecular hydrogen bonds (2.640(1) and 2.652(1) Å) with hydroxyl groups (Fig. 1, a hydrogen bond shown as a dotted line). The solvent methanol molecules form intermolecular O-H∙∙∙O hydrogen bonds of 2.739(1) and 2.696(1) Å with the same monocoordinated isobutyrates. The spectroscopic, thermogravimetric and magnetic properties have been also studied and all data will be discussed.   Acknowledgments. The authors acknowledge the financial support from the DAAD (O. I. B.), SCOPES (IZ73ZO_152404/1) and the Grant for Young Scientists (Project 15.819.02.03F)