Immunotheranostics will be an important development in the future of nuclear medicine and medical oncology. It describes the synergy of theranostic procedures in nuclear medicine and immune oncology (IO) treatment. In brief, it takes advantage of molecular imaging and subsequent targeted modulation of the-in most cases immunosuppressive-tumor microenvironment (TME) by diagnostic and therapeutic radioisotopes. This is of high importance since only a fraction of patients receiving IO is currently being cured by this exciting therapy option. We therefore envision the concept of immunotheranostics as a powerful mean to augment the success of IO treatment in the future and thus the urgent need to further develop the interaction and joint action of nuclear medicine and medical oncology for substantially improved therapy outcome for cancer patients.