A novel polythioetheramide was synthesized from allylamine and 3-mercaptopropionic acid with a free-radical initiator. The thioether and amide linkages are formed from the free-radical addition of -SH group to double bond and the condensation between -NH2 and -COOH, respectively. The free-radical addition gives almost exclusively anti-Markovnikov product. The resulting polymer has a glass-transition temperature of 8.5 degrees C and a melting point of 145 degrees C. Though the introduction of the thioether linkages increases flexibility, the polymer retains good solvent resistance.