Poly(ethylene terephthalate) pellets were subjected to various amine solutions under hydrothermal conditions in a semibatch reactor. Methylamine, ethylamine, dirnethylamine, trimethylamine, ammonia, and sodium hydroxide were examined at 473 K and 10 MPa at concentrations of 0.6 mol/kg. The effects of the amine species on reaction rates and monomer yields were compared. For all solvents examined in the present study, the reactions were expressed by a surface reaction model, i.e., the 2/3rd-order reaction kinetics with respect to unreacted polymer mass. The reaction rates with the four amines were not very different and were similar to that with NaOH at the same concentration; but, they were faster than the rate with ammonia. When the reaction was conducted with trimethylamine, the yields of monomers and total yields of terephthalic acid and ethylene glycol were very close to the theoretical values. However, those with dimethylamine, ethylamine, and methylamine were slightly lower with intermediate products found in the product solutions.