The development of innovative nanomaterials for cancer detection has received a lot of attention in recent years. Because of their special qualities and adaptability, polymer core-shell nanoconstructs have become one of the most promising options among them. The review starts off with a summary of the various polymer kinds that are utilized as core and shell materials, emphasizing their benefits and drawbacks. The synthesis of polymer core-shell nanoconstructs using different techniques is then covered, including layer-by-layer assembly, template synthesis, and emulsion polymerization. Polymer core-shell nanoconstructs, which combine therapeutic and diagnostic functions into a single nanostructure, have emerged as promising platforms for cancer theragnostic applications. Development, synthesis, and potential uses of polymer core-shell nanoconstructs for cancer detection and therapies have advanced recently, and this review summarizes these developments. A number of benefits come with the core-shell architecture, such as improved stability, regulated drug release kinetics, and the capacity to combine numerous imaging and therapeutic agents at once. Several polymerization methods, including layer-by-layer assembly, polymer blending, and emulsion polymerization, have been used to precisely control the size, shape, and surface characteristics of these nanoconstructs. Moreover, surface modification techniques allow for the targeted destruction of cancer cells, increasing therapeutic efficacy and reducing off-target effects. Additionally, to produce synergistic effects and overcome multidrug resistance, therapeutic agents such as nucleic acids, photothermal agents, and chemotherapeutic drugs can be conjugated or encapsulated onto the nanoconstructs. Polymer core-shell nanoconstructs have the potential to revolutionize personalized cancer therapy through precise diagnosis, targeted drug delivery, and real-time treatment efficacy monitoring in the clinic. Before being widely used in clinical settings, issues like biocompatibility, systemic toxicity, and regulatory approval must be resolved. All things considered, polymer core-shell nanostructures offer a flexible platform for developing cancer therapeutics and enhancing patient outcomes.