Background <p>Nanomaterials have received significant attention in bioimaging and theranostics due to their unique physicochemical features and multifunctional capabilities. These materials are very useful in cancer diagnosis and treatment because they provide increased sensitivity, precision targeting, and little invasiveness.</p> Main Text <p>Different nanomaterials, including mesoporous silica, gold, silver, carbon-based nanoparticles, and hybrid structures, are designed to function as targeted drug carriers, biosensors, and high-resolution imaging agents. The combination of different imaging modalities with therapeutic functions has resulted in the development of “smart” nanoparticles that can diagnose and cure diseases at the same time, boosting treatment efficacy and lowering systemic toxicity. This review discusses recent advances in nanomaterials for cancer theranostics, focusing on critical parameters such as biocompatibility, surface changes, controlled drug release, and stimulus-responsive systems.</p> Conclusion <p>Future prospects are also discussed, with a focus on the possibility for personalised treatment via bioinspired designs, combination therapies, and integration with technology such as artificial intelligence with imaging instruments. The review aims to emphasise nanotechnology’s revolutionary role in improving diagnostic accuracy and therapeutic efficiency, paving the path for more precise and personalised cancer treatment.</p>