Malignant tumours continue to present a significant challenge to global public health, with early theranostics serving as critical strategies to enhance patient prognosis. Advancements in nanotechnology have catalyzed the development of innovative approaches, where the synergy between nanomaterials and therapeutic modalities offers promising solutions to overcome the limitations of traditional cancer treatments. Among these innovations, metal-organic frameworks (MOFs) have emerged as a focal point of research in cancer theranostics. Their three-dimensional porous structure, precisely tunable pore sizes, excellent biocompatibility, and versatile surface functionalization make them particularly attractive. Additionally, the controllable synthesis and ordered structural characteristics of MOFs enable the integration of functional nanoparticles through hierarchical assembly strategies, resulting in heterojunction systems with various configurations, such as "core-shell", "moon-star", "yolk-shell", and "Janus" structures. These materials demonstrate synergistic effects in cancer treatment, often outperforming single MOF materials. This review comprehensively discusses the latest advancements in single and double metal MOFs, as well as their heterojunction-derived materials, in tumour visualization, targeted therapy, and integrated theranostics. The insights provided offer important theoretical foundations and technical references for the clinical translation of MOF-based nanomedicines.