In the1980s, radiolabeled cells helped understand the pathology of hemato-oncology. In the 1990s, preclinical trials evaluated radiolabeled immunotherapy with monoclonal antibodies (MoAbs) such as anti-CD20 agents labeled with Iodine-131 (Bexxar) or Yttrium-90 (Zevalin). Due to the safe and durable responses of radiolabeled MoAbs, the Food and Drug Administration approved these agents in the 2000s. Despite radioimmunotherapy's long journey, its application has recently decreased. This review will discuss the historical timeline of radioimmunotherapy, debate on advantages and difficulties, and explore trials. We will examine future directions of radioligand therapy in hemato-oncology, considering emerging molecules that may become the next theragnostic trend.