In the early 2000s, major clinical trials provided evidence of a favorable outcome from antibody-mediated radioimmunotherapy for hematologic neoplasms, which then led to Food and Drug Administration approval. For instance, the theranostic armamentarium for the referring hematooncologist now includes90Y-ibritumomab tiuxetan for refractory low-grade follicular lymphoma or transformed B-cell non-Hodgkin lymphoma, as well as131I-tositumomab for rituximab-refractory follicular lymphoma. Moreover, the first interim results of the SIERRA phase III trial reported beneficial effects from the use of131I-anti-CD45 antibodies (Iomab-B) in refractory or relapsed acute myeloid leukemia. During the last decade, the concept of theranostics in hematooncology has been further expanded by C-X-C motif chemokine receptor 4–directed molecular imaging. Beyond improved detection rates of putative sites of disease, C-X-C motif chemokine receptor 4–directed PET/CT also selects candidates for radioligand therapy using β-emitting radioisotopes targeting the identical chemokine receptor on the lymphoma cell surface. Such image-piloted therapeutic strategies provided robust antilymphoma efficacy, along with desired eradication of the bone marrow niche, such as in patients with T- or B-cell lymphoma. As an integral part of the treatment plan, such radioligand therapy–mediated myeloablation also allows one to line up patients for stem cell transplantation, which leads to successful engraftment during the further treatment course. In this continuing education article, we provide an overview of the current advent of theranostics in hematooncology and highlight emerging clinical applications.