Dopamine is a neurotransmitter commonly used in clinical treatment. Polydopamine (PDA) has excellent histocompatibility and biosafety and can efficiently convert near-infrared reflection (NIR) to thermal energy. In this study, PDA was used as a promising carrier, and pH-responsive polymer-coated drug-loaded PDA nanoparticles (NPs; doxorubicin@ poly(allylamine)-citraconic anhydride [Dox@PAH-cit]/PDA NPs) were developed. As expected, the Dox@PAH-cit/PDA NPs exhibited excellent photothermal efficiency. In addition, at a low pH condition, the loaded Dox was released from the NPs due to the amide hydrolysis of PAH-cit. Upon NIR exposure (808 nm), the temperature of the NP solution rapidly increases to kill tumor cells. Compared with unbound chemotherapy drugs, the NPs have a stronger cell uptake ability. In vivo, the PDA NPs were able to efficiently accumulate at the tumor location. After intravenous administration and NIR exposure, tumor growth was significantly inhibited. In summary, the present investigation demonstrated that the Dox@PAH-cit/PDA NPs presented highly effective photothermal chemotherapy for prostate cancer.