A metallocene catalyst system, primarily the bis(eta(5)-cyclopentadienyl)cobalt (Cp2Co) combined with n-butyllithium (n-BuLi), was found to be active for the hydrogenation of polystyrene-b-polybutadiene-b-polystyrene (SBS) block copolymer. Data from the UV spectroscopy of the catalyst system indicated that one of the Cp ligand in the original Cp2Co was substituted by the butyl group forming a CpCoBu as the major catalytic species. The kinetics of the hydrogenation reaction were studied by monitoring the extent of saturation of double bonds on the polybutadiene segment of the copolymer using FTIR spectroscopy. The temperature dependence of the hydrogenation rate was analyzed and the activation energy was determined as 14.11 kcal/mol of the double bond.