Nanometer-sized and stable thiolate-protected cobalt clusters were synthesized by a wet chemical method, leading to a pink solution with well-defined optical activity (ultraviolet–visible) and photoluminescence. The cobalt cluster core of ∼1.3 nm size was metallic (as indicated by scanning transmission electron microscopy, scanning tunneling microscopy, X-ray photoelectron spectroscopy, electron-energy loss spectroscopy) and was surrounded by a specific configuration of thiolate staples (according to Raman spectra, Fourier transfrom infrared spectroscopy, X-ray absorption fine structure, matrix-assisted laser desorption ionization) that is similar to that of corresponding gold clusters.