Cysteine is found to accelerate electroless nickel (EN) deposition and hydrogen evolution simultaneously. Changes in the activation energy of the EN reaction and the electrochemical behaviour of the EN bath due to the presence of cysteine were studied. The composition of the deposit formed was determined by XPS. The results show that the activation energy of the EN reaction is decreased when cysteine is added to the bath, and also that cysteine only influences the anodic process and has no direct effect on the cathodic process. The high resolution XPS spectra show that cysteine is adsorbed in the surface layer, and S2- in the inner layer of the deposit. It is deduced that cysteine may participate in the formation of a reactive intermediate and facilitate the oxidation of H2PO2-, which results in the acceleration of EN plating.