To achieve molecular packing of protic-functionalized helical polymers in aqueous solution, we synthesized an amphiphilic helix-coil-helix triblock copolymer (triBCP) composed of polystyrene and dihydroxyl-functionalized polyisocyanates. Poly(3-(glycerylthio)propyl isocyanate)-block-polystyrene-block-poly(3-(glycerylthio)propyl isocyanate), P3GPIC-b-PSt-b-P3GPIC, was synthesized by postpolymerization modification. The bidirectional anionic block copolymerization of styrene (St) and allyl isocyanate (AIC) yielded triBCPs, poly(allyl isocyanate)-block-polystyrene-block-poly(allyl isocyanate)s (PAIC-b-PSt-b-PAICs), with well-controlled molecular weights (M-n = 5.60-99.9 kDa) and narrow dispersities (D = 1.14-1.18). Of them, one with the lowest MW (M-n = 5.60 kDa, D = 1.14), which was highly organic-soluble, was utilized in the thiol-ene click reaction between allyl group and 1-thioglycerol, producing P3GPIC-b-PSt-b-P3GPIC. The amphiphilic P3GPIC-b-PSt-b-P3GPIC self-aggregated to form spherical vesicles with an average hydrodynamic diameter of 170 nm in aqueous solution, demonstrating that hydrophilic-helical P3GPIC blocks well interacted with water media maintaining their intermolecular packing.