The continuing increase of cancer morbidity and death rate requires efficient therapeutic strategies. The traditional chemotherapy usually fails to treat cancer or prolong survival rate due to its toxicity to normal cells, side effects and lack of targeting capacity. In recent years, nanomaterials have shown great potentials to treat various cancers efficiently. Graphene-based nanomaterials, especially graphene oxide (GO) and reduced GO (rGO), have arisen as promising candidates for cancer therapy. Due to their unique physicochemical and optical properties including the extremely large surface area, modifiable active groups, great biocompatibility and strong photothermal effect, they can act either as tunable carriers or active agents for advanced chemotherapeutics delivery and cancer therapy. Therefore, combing the photothermal therapy, targeted drug delivery and chemotherapy would have great potentials for efficient cancer therapy. Herein, the comprehensive understandings of the physicochemical properties and various anti-cancer applications of GO and rGO as drug delivery systems or photothermal agents are described. Also, the concerns in using GO and rGO, such as the nano-protein interaction, and possible solutions are discussed.