A new octanuclear iron(III) isobutyrate cluster [Fe8O3(is)6(O2CH)3(tea)(teaH)3]·teaH3·(CH3)2CO (1) (where His = isobutyric acid; teaH3 = triethanolamine) has been prepared by the interaction of smaller trinuclear isobutyrate cluster [Fe3O(is)6(H2O)3](NO3)·2(CH3CN)∙2(H2O) with s-triazine and triethanolamine. Single-crystal X-ray analysis revealed that 1 crystalizes in the triclinic space group P-1 and comprises octanuclear [Fe8O3(is)6(O2CH)3(tea)(teaH)3] clusters and solvate teaH3 and acetone molecules. The iron centers in the {Fe8} core are bridged by three μ4-oxo atoms, and peripheral ligation of the core is provided by six isobutyrates and four triethanolamine ligands. Formate group is completed the coordination sphere of three metal atoms. Cluster 1 has been also characterized by elemental, infrared spectroscopy and thermogravimetric analyses.