Molecular radiopharmaceuticals based on bioconjugates of chelators with peptides and proteins have had significant clinical impact in the diagnosis and treatment of several types of cancers. In the 1990s, indium-111 and yttrium-90 labeled chelator-peptide/protein conjugates established the clinical utility of these radiopharmaceuticals for receptor-targeted γ-scintigraphy imaging and systemic radiotherapy. Second-generation bioconjugates based on peptides targeting the somatostatin II receptor and the prostate-specific membrane antigen are now widely used for management of neuroendocrine and prostate cancer, respectively. These bioconjugates are typically radiolabeled with gallium-68 for imaging of target receptor expression with positron emission tomography, and the β--emitter, lutetium-177, for targeted radiotherapy. Innovations in radioisotope technology and biomolecular therapies are likely to drive the future clinical development of radiopharmaceuticals based on radiometals. New chelator-peptide and chelator-protein bioconjugates will underpin nuclear medicine advances in molecular imaging and radiotherapy.