Aqueous Au nanoparticles (NPs) are employed as the building blocks to construct chainlike self-assembly architectures, which greatly enhance the photothermal performance at 808 nm. Biocompatible polypyrrole (PPy) is further adopted as the package material to coat Au NP chains, producing stable photothermal agents. As a result of contributions from chainlike Au, the PPy shell, as well as the Au-PPy composite structures, the capability of photothermal transduction at 808 nm is greatly enhanced, represented by the high photothermal transduction efficiency up to 70%. Primary animal experiment proves that the current composite photothermal agents are efficient in inhibiting tumor growth under an 808 nm irradiation, showing the potentials for in vivo photothermal therapy.