Theranostics in nuclear medicine refers to personalized patient management that involves targeted therapy and diagnostic imaging using a single or combination of radionuclide (s). The radionuclides emit both alpha (α) or beta (β-) particles and gamma (γ) rays which possess therapeutic and diagnostic capabilities, respectively. However, the production of these radionuclides often faces difficulties due to high cost, complexity of preparation methods and that the products are often sourced far from the healthcare facilities, hence losing activity due to radioactive decay during transportation. Subject to the availability of a nuclear reactor within an accessible distance from healthcare facilities, neutron activation is the most practical and cost-effective route to produce radionuclides suitable for theranostic purposes. Holmium-166 (166Ho), Lutetium-177 (177Lu), Rhenium-186 (186Re), Rhenium-188 (188Re) and Samarium-153 (153Sm) are some of the most promising neutron-activated radionuclides that are currently in clinical practice and undergoing clinical research for theranostic applications. The aim of this paper is to review the physical characteristics, current clinical applications and future prospects of these neutron activated radionuclides in theranostics. The production, physical properties, validated clinical applications and clinical studies for each neutron-activated radionuclide suitable for theranostic use in nuclear medicine are reviewed in this paper.