A new one pot synthetic method has been developed for preparing amphiphilic block copolymers. The method makes use of episulfide anionic polymerization for generating symmetric or asymmetric tri- or multiblock copolymers with living mechanism. Important features of the method are (a) the use of in situ generated thiolates, which ensures reproducibility in the initiator concentration; (b) the mild character of the reactive species; therefore, also sensitive bioactive groups could be easily incorporated into the polymer structure; (c) the tolerance to impurities in the reagents and the one pot character, which allow the use of the method also by operators with limited skills in organic synthesis.