Design and synthesis of polynuclear complexes of 3d metals attract tremendous interest, because of their promising physical and catalytic properties as well as their potential to function as single-molecule magnets (SMMs), which may have applications in information storage and quantum computing. The reaction of cobalt(II) isobutyrate with triethanolamine (H3tea) and azide ligands in MeCN media under heating lead to a new pentanuclear mixed-valent [CoIICoIII4(is)2(N3)4(Htea)4](His) coordination cluster (Figure 1). A single crystal X-ray diffraction analysis revealed that the compound represents solvate and crystalizes in the orthorhombic Pbca space group with a = 28.075(1), b = 10.4998(3), c =36.2047(1) Å, and V = 10672.7 Å3. The Co(III) atoms are bridged in dimers (Co1 and Co2; Co3 and Co4) by two twice deprotonated Htea2- and one monodeprotonated isobutyrate ligands. Each of Co(III) atoms is six-coordinated adopting an octahedral N2O4 geometry by an O atom from isobutyrate, three O atoms and a N atom of two Htea2- ligands, and a N atom from the azide anion. The Co(II) atom (Co5) adopts a tetrahedral O4 surrounding due to coordination of two dimers through O atoms from aminoalcohol ligands and results in a pentanuclear cluster formation. The shortest Co(III)…Co(III) separations in the cluster are 2.819 and 2.828 Å, and Co(II)…Co(III) separations are in the range of 3.129 - 3.181 Å.