Noble metal nanomaterials have been extensively explored in cancer diagnostic and therapeutic applications owing to their unique physical and chemical properties, such as facile synthesis, straightforward surface functionalization, strong photothermal effect, and excellent biocompatibility. Herein, we summarize the recent development of two-dimensional(2D) Pd-based nanomaterials and their applications in cancer diagnosis and therapy. Different synthetic strategies for Pd nanosheets and the related nanostructures, including Pd@Au, Pd@Ag nanoplates and mesocrystalline Pd nanocorolla, are first discussed.Together with their unique properties, the potential bioapplications of these 2D Pd nanomaterials are then demonstrated. With strong absorption in near-infrared(NIR) region, these nanomaterials have great potentials in cancer photothermal therapy(PTT). They also readily act as contrast agents in photoacoustic(PA) imaging or X-ray computed tomography(CT) to achieve image-guided cancer therapy. Moreover,significant efforts have been devoted to studying the combination of PTT and other treatment modalities(e.g., chemotherapy or photodynamic therapy) based on Pd nanomaterials. The remarkable synergistic or collaborative effects to achieve better therapeutic efficacy are discussed as well. Additionally, the biosafety of 2D Pd-based nanomaterials in vitro and in vivo was evaluated. Finally, challenges for the applications of Pd-based nanomaterials in cancer diagnosis and therapy, and future research prospects are highlighted.