A hydrogenated styrene-butadiene copolymer (HSBR) was prepared by a diimide reduction of SBR in the latex stage. The influence of the styrene content on various reaction parameters, namely, time, temperature, and concentration of the reactants and the catalyst was studied. A comparatively lower temperature, longer time, lesser amount of hydrogen peroxide, acid higher amount of the catalyst are required to optimize the hydrogenation reactions of SBR with a higher styrene content. The diimide reduction of SBR is first order with respect to the olefinic substrate and the apparent activation energy increases with increase in the styrene level. All the hydrogenated copolymers were characterized with the help of IR, NMR, and DSC. The TGA data indicate a higher thermal stability of HSBR as compared to SBR in nitrogen, although an anomalous behavior is observed in air due to crosslinking and oxidation.