Gold nanocages represent a novel class of nanostructures, well-suited for biomedical applications. They can be readily prepared via the galvanic replacement reaction between silver nanocubes and chloroauric acid. Their optical resonance peaks can be easily and precisely tuned to the near-infrared region from 650–900 nm, the transparent window for blood and soft tissue. Furthermore, their surface can be conveniently conjugated with various ligands for targeting cancer. In this feature article, we highlight recent advances in the large-scale synthesis of gold nanocages and their applications in cancer diagnosis and treatment. Specifically, we have scaled up the production of gold nanocages for in vivo studies and evaluated their tumor targeting capabilities. We have also demonstrated their use as contrast agents for photoacoustic tumor imaging and the mapping of sentinel lymph node, as photothermal transducers for cancer treatment, and as smart carriers for controlled release with a near-infrared laser.