A straightforward approach based on thiol-ene click chemistry was used to prepare novel functional polyesters containing amino groups. First, a series of well-defined alkene-functional poly(ε-caprolactone)s were prepared by ring-opening polymerization of α-allyl-ε-caprolactone with ε-caprolactone in toluene and in bulk using tin 2-ethylhexanoate as catalyst. These functional polyesters were fully characterized by 1H NMR, GPC, and MALDI-TOF MS. The resulting random copolyesters were obtained with a wide range of molar masses from 3000 to 50[thin space (1/6-em)]000 g mol−1 and a good incorporation of the α-allyl-ε-caprolactone monomer unit. Then, thiol-ene reaction of alkene-functional PCL with the 2-(Boc-amino)ethanethiol was used to prepare efficiently polyesters bearing protected amino groups without chain degradation. Finally, cationic and water-soluble polyesters bearing free amino groups were recovered by cleavage of the Boc protecting group. These aminated polyesters were characterized by 1H NMR in deuterated water.