Two-dimensional (2D) materials have brought about significant technological advancements in the field of biomaterials. Transition metal carbides and/or nitrides (MXenes) have a planar structure educed from their corresponding parent MAX phase by selective etching of ‘A’ and further delamination. Since the first MXene was reported in 2011, MXenes now comprise a rapidly growing family of 2D materials, having attracted extensive attention from researchers. Owing to their excellent electronic properties, outstanding photothermal conversion performance, high specific surface area, good biocompatibility, and low toxicity, MXenes have shown a good application prospect in tumor theranostics. This paper reviews substantive findings of the original researches focused on the preparation, property and application in tumor theranotics, including recent advances, challenges and future perspectives of MXenes. Firstly, we briefly summarize the preparation methods and property of MXenes, including HF acid method, fluoride salt method, molten salt method, alkali-assisted hydrothermal method, and chemical vapor deposition method, as well as stability, mechanical, optical, and electrical properties. Secondly, we focus on the application of MXenes in photothermal therapy and combined therapy. The usual method is to combine photothermal therapy, photodynamic therapy and chemotherapy to carry out multi-modal combined treatment of tumors. The combined therapy can also be improved by constructing surface nanopores of MXenes and loading chemotherapy drugs in them. Furthermore, enhanced MXenes synergistic therapeutic effect on tumor and reduced toxic side effects on normal tissue can be endued by active targeting technology. In addition, the preparation of multifunctional MXenes composite nanomaterials to obtain radiation treatment and imaging capabilities such as computed tomography scans and magnetic resonance imaging, can establish an integrated platform for MXenes theranostics. Finally, we briefly introduced other applications of MXenes in biomedicine which are beneficial to tumor theranostics, and elaborate the current challenges and future development prospects of MXenes in cancer theranostics.