The title compound, [Os(CHAsS)(CO)] or [Os{As(CHSCH)}(CO)], comprises a triangle of Os atoms, two of which are bonded to four carbonyl ligands. The third Os atom is bound to three carbonyl ligands, and the arsine ligand [As(CHSCH)] occupies the equatorial position. In the crystal, the mol-ecules are linked by C-H⋯O hydrogen bonds. To further analyse the inter-molecular inter-actions, a Hirshfeld surface analysis was performed. Two out of the three methyl-sulfanyl groups are disordered over two sites with final refinement occupancy ratios of 0.612 (12):0.388 (12) and 0.620 (9):0.380 (9).