Liquid natural rubber (LNR) is a depolymerized natural rubber (NR) which consists of shorter polymeric chains and lower molecular weight (M_w < 10⁵). Hydrogenated LNR (HLNR) was synthesized via the thermal decomposition of p‐toluenesulfonyl hydrazide (TSH) or 2,4,6‐trimethylbenzenesulfonyl hydrazide (MSH). The LNR and HLNR structures were characterized by Fourier‐transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies. The percentage of hydrogenation was calculated from NMR spectrum. The optimum percentage of hydrogenation (>90%) was achieved by manipulating the reaction parameters such as sources of diimide, TSH concentration, solvent, and reaction time. The optimum condition was 3 : 1 weight ratio of TSH/LNR in o‐xylene at 130°C in 4‐hour reaction period.