Direct synthesis of well-defined heterotelechelic polymers having functional groups allowing the chemoselective bioconjugations would be desirable to enhance the versatility of polymers for bioconjugations and bio-related applications. Considering this, well-defined a-azide, ?- dithiopyridine polymers were synthesized in one step via the reversible addition-fragmentation chain transfer (RAFT) polymerization. The telechelic functionality (i.e., mole ratio of the ?-dithiopyridine to the ?-azide end group) of polymers was above 0.90, indicating the efficient generation of well-defined heterotelechelic polymers. The heterotelechelic functionality for chemoselective bioconjugations was tested by reacting a-azide, ?-dithiopyridine poly(NIPAAm) with model biomolecules, i.e., biotin/avidin, glutathione, and bovine serum albumin, via click and thiol-disulfide exchange chemistries. Near-stoichiometric conjugation with biomolecules indicated high functionality of the polymer end groups.