Nonmagnetic inorganic/organic core-shell nanoconstructs are the advanced, versatile platform in treating cancer as theranostics. Theranostics is an emerging tool in cancer treatment; it is a combination technique in which a drug is loaded in a suitable formulation, which can diagnose images, and the drug will target the cells. The core is made of nonmagnetic inorganic material such as mesoporous silica, gold, quantum, cerium oxide, silica, titanium dioxide, and calcium phosphate; and the shells are made of organic materials such as liposomes, polymer, dendrimer, albumin, chitosan, cyclodextrin, and protein-based nanoparticles. In addition to their versatility, these nanoconstructs are low in toxicity, stable, biocompatible, and environmentally friendly, ensuring safety in their use. They have excellent imaging techniques and inbuilt fluorescence properties, which help in photothermal imaging to diagnose cancer cells. Inorganic nonmagnetic cores such as gold and quantum have photothermal therapy, which can synergistically treat cancer cells. The organic shell can undergo surface modification such as stimuli-responsive, protein-peptide binding, targeting ligand, grafting and chemical electrostatic interaction, and treatment with the cancer cells. The organic shell can also target the tumor cells with ligands such as antibodies and folic acid and conjugate to the shell for active targeting by stimuli that are responsive to release drugs in a controlled manner. The applications are dual imaging, targeted drug delivery, photothermal therapy, thermos-chemotherapy, enhanced biocompatibility, real-time monitoring, and multimodal theranostic. However, the studies have proved precision and efficient results in preclinical studies, and challenges such as addressing the regulatory scalability from batch to batch that need to be focused on for implementation in a clinical study. This chapter briefs the types, surface modification, properties, and application of cancer theranostics of core-shell nanoconstructs.