Metal chalcogenide clusters are structural motifs utilized, for example, in enzymatic active sites, catalysts, and optical/optoelectronic materials. Among non-biomimetic cluster complexes, those consisting of cobalt and sulfur are particularly attractive due to their potential as catalysts, electrocatalysts, semiconducting materials, and so forth. Moreover, intriguing properties have been reported for cobalt sulfide nanoparticles, giving rise to interest in cobalt–sulfur cluster complexes. However, synthetic routes to cobalt–sulfur cluster complexes are quite limited and their structural diversity is very low. Thus, development of facile cobalt–sulfur sources and terminal ligands is strongly desired. In this presentation, we discuss the selective synthesis of the well-defined Co₈S₁₅ cluster complex starting from a cobalt trisulfide complex. The precursor cobalt trisulfide complex served as a cobalt–sulfur source as well as a powerful sterically templating terminal ligand. A corner-sharing double-cubane-like cobalt–sulfur cluster was selectively synthesized from an easily prepared cobalt trisulfide complex of pentaaryl[60]fullerene. The obtained cluster contained two Co₄S₅ cubane-like units coordinated by thiolate and disulfide ligands. The bowl-shaped steric template as well as the metastable cobalt trisulfide moiety played important roles in the exclusive cluster formation. Crystallographic, electrochemical, and magnetic measurements elucidated a mixed-valence nature of the cluster with two high-spin cobalt(II) centers. The present study will provide new opportunities for development of artificial functional metal–sulfur cluster complexes for various applications.