In this paper, we demonstrated that commercially available triblock copolymers such as polystyrene-b-polybutadiene-b-polystyrene (SBS) and polystyrene-b-polyisoprene-b-polystyrene (SIS), used as thermoplastic elastomers, exhibit autonomic self-healing behavior at room temperature without any chemical reaction even after cutting into two separate pieces. The healing efficiency is improved by immediate recombination after cutting, and is attributed to the destruction of the microstructure, i.e., polystyrene domains, leading to marked molecular mobility. Furthermore, quenched samples with obscure phase-separation exhibit good healing behavior. Finally, SBS has better healing efficiency than SIS because the solubility parameter of polybutadiene is closer to that of polystyrene than that of polyisoprene; to some extent, the solubility parameter is responsible for enhanced molecular motion owing to the mutual dissolution of both components.