Chemoselective stepwise coupling between living polymers and a heterobifunctional linking agent is shown to be a versatile, facile, and efficient methodology for block copolymer synthesis. This protocol is based on the quantitative formation of the end-functionalized precursor in the first coupling step. In this proof-of-concept study, we investigate the behavior of specific macroanions, prepared through living anionic polymerization (LAP). Nevertheless, the applicability range is becoming exceptionally wide upon transformation reactions, e.g., by tailoring the chain-termini nucleophilicity via endcapping. This novel protocol will considerably expand the limits of LAP, rendering viable the construction of advanced and tailor-made materials via an effortless pathway.