Combining informative imaging methodologies with effective treatments to destroy tumors is of great importance for oncotherapy. Versatile nanotheranostic agents that inherently possess both diagnostic imaging and therapeutic capabilities are highly desirable to meet these requirements. Here, a simple but powerful nanoplatform based on polydopamine-coated gold nanostar (GNS@PDA), which can be easily diversified to achieve various function extensions, is designed to realize functional and anatomical imaging-guided photothermal oncotherapy. This nanoplatform intrinsically enables computed tomography/photoacoustic/two-photon luminescence/infrared thermal tetramodal imaging and can further incorporate fibroblast activation protein (FAP, a protease highly expressed in most of tumors) activatable near-infrared fluorescence imaging and Fe3+-based magnetic resonance imaging for comprehensive diagnosis. Moreover, GNS@PDA exhibits excellent photothermal performance and efficient tumor accumulation. Under the precise guidance of multimodal imaging, GNS@PDA conducts homogeneous photothermal ablation of bulky solid tumors (∼200 mm3) in a xenograft mouse model. These results suggest great promise of this extendable nanoplatform for cancer theranostics.