In photothermal therapy (PTT), the photothermal conversion of the second near-infrared (NIR-II) window allows deeper penetration and higher laser irradiance and is considered a promising therapeutic strategy for deep tissues. Since cancer remains a leading cause of deaths worldwide, despite the numerous treatment options, we aimed to develop an improved bionic nanotheranostic for combined imaging and photothermal cancer therapy. We combined a gold nanobipyramid (Au NBP) as a photothermal agent and MnO2 as a magnetic resonance enhancer to produce core/shell structures (Au@MnO2; AM) and modified their surfaces with homologous cancer cell plasma membranes (PM) to enable tumour targeting. The performance of the resulting Au@MnO2@PM (AMP) nanotheranostic was evaluated in vitro and in vivo. AMP exhibits photothermal properties under NIR-II laser irradiation and has multimodal in vitro imaging functions. AMP enables the computed tomography (CT), photothermal imaging (PTI), and magnetic resonance imaging (MRI) of tumours. In particular, AMP exhibited a remarkable PTT effect on cancer cells in vitro and inhibited tumour cell growth under 1064 nm laser irradiation in vivo, with no significant systemic toxicity. This study achieved tumour therapy guided by multimodal imaging, thereby demonstrating a novel strategy for the use of bionic gold nanoparticles for tumour PTT under NIR-II laser irradiation.