2-Aminoethanol was decomposed in sub- and supercritical water, with/without hydrogen peroxide. The conversion of total organic carbon (TOC) and the yields of ammonia and carbon dioxide were found to be enhanced under supercritical conditions of water, when compared with those under subcritical conditions. The yield of ammonia was found to be correlated with yield of carbon dioxide, nearly, irrespective of the presence of hydrogen peroxide, while conversions of 2-aminoethanol and TOC were significantly affected by adding hydrogen peroxide.