[Mn(CO)₄{S₂CNMe(CH₂CO₂H)}], 1, is shown to be a CO releasing molecule providing at least three moles CO per mole of compound. The mechanism of CO loss is dissociative and reversible and was investigated using Gaussian 09 calculations. The reversible binding of CO results in a relatively stable solution of the compound, while in the presence of a CO receptor or a ligand to prevent the rebinding of CO, the CO is lost rapidly. The X-ray structure was determined.