Nanomedicine integrates different functional materials to realize the customization of carriers, aiming at increasing the cancer therapeutic efficacy and reducing the off-target toxicity. However, efforts on developing new drug carriers that combine precise diagnosis and accurate treatment have met challenges of uneasy synthesis, poor stability, difficult metabolism, and high cytotoxicity. Metal-phenolic networks (MPNs), making use of the coordination between phenolic ligands and metal ions, have emerged as promising candidates for nanomedicine, most notably through the service as multifunctional theranostic nanoplatforms. MPNs present unique properties, such as rapid preparation, negligible cytotoxicity, and pH responsiveness. Additionally, MPNs can be further modified and functionalized to meet specific application requirements. Here, the classification of polyphenols is first summarized, followed by the introduction of the properties and preparation strategies of MPNs. Then, their recent advances in biomedical sciences including bioimaging and anti-tumor therapies are highlighted. Finally, the main limitations, challenges, and outlooks regarding MPNs are raised and discussed.