Hetero-multinuclear metal complexes are a promising class of compounds applicable to photoluminescence, magnetism, and catalysis. In this work, we have developed a synthetic method for hetero-tetranuclear metal complexes by combining advantages of site-selective redox switching and transmetalation. First, a homo-tetranuclear (Co4I)-I-II complex was converted to a mixed-valence (CoCo3II)-Co-III complex by site-selective oxidation, which was then transmetalated from Co-II to N-II to form a heterometallic (CoCo3II)-Co-III complex. Finally, a (CoCo3II)-Co-III complex was synthesized by metal-selective reduction on the Co' site. The basic structural frameworks of the main products in the whole process starting from the Co-4(II) complex are isostructural. Notably, the (CoCo3II)-Co-III complex was not accessible by direct mixing of ligand, Co-II, and Ni-II. This method would provide an alternative strategy for highly selective synthesis of hetero-multinuclear metal complexes.