Photothermal therapy is a promising phototherapeutic modality that has been widely studied in cancer therapy. However, because of the influence of heat shock protein (HSP), the therapeutic efficacy of photothermal therapy (PTT) is significantly suppressed. To improve the therapeutic efficacy, different tumor-specific therapeutic modalities have been chosen to combine with PTT. However, most of them rely on endogenous stimuli to trigger combination therapy, which may suffer from the issue of incomplete activation. Herein, we develop a PTT/thermodynamic combination therapeutic nanosystem whose therapeutic process is controlled by an external stimulus, near-infrared (NIR) light. The nanosystem (ADPPTN) is composed of a second NIR (NIR-II) fluorescent semiconducting polymer (SP) (DPPT) as the core, and a carboxyl group-decorated amphiphilic copolymer (PSMA-PEG) as the shell with an azo-containing compound (AIPH) loaded via electrostatic interaction. Under 808 nm laser irradiation, DPPT can generate heat to conduct PTT, while the elevated temperature may further trigger the release of AIPH radicals, conducting thermodynamic therapy (TDT). In addition, the NIR-II fluorescence signal emitted from DPPT can light the tumor. Compared with the nanoparticles without AIPH (DPPTN), ADPPTN has better anticancer efficacy under laser irradiation both in vitro and in vivo. Thus, our study provides an NIR-II fluorescence imaging-guided PTT/TDT combination therapeutic nanosystem for efficient cancer theranostics.