The development of innovative, easy to implement strategies for polymer synthesis and modification contributes to pushing back the limits of macromolecular engineering. In this context, thiolactones were highlighted as a new powerful "click" strategy involving an amine-thiol-ene conjugation. In order to further explore the potential of thiolactone chemistry for the field of reversible-deactivation radical polymerization (RDRP), we have developed a toolbox of y-thiolactone-based RDRP agents including xanthates, bromides, and an alkoxyamine. These RDRP agents were used for the polymerization of more activated and less activated monomers using appropriate RDRP techniques such as RAFT/MADIX, ATRP, and NMP. Well-defined thiolactone-terminated polymers were obtained and characterized for different degrees of polymerizations. An example of thiolactone-telechelic PNIPAM using a thiolactone-based xanthate and an co-end-chain cyclization strategy was reported. The great reactivity of the thiolactone end-group for postpolymerization modification was proven using primary amines such as benzylamine or propargylamine, which ring-opened the thiolactone with subsequent thiol-thiolsulfonate reaction to scavenge the generated thiol. The original S-naphthalene ethanethiosulfonate was used to give fluorescence properties to the polymers.