This review explores the vital role of radioisotopes in contemporary healthcare. Radioisotopes, atoms with unstable nuclei emitting ionizing radiation, have become invaluable tools in modern medicine. Their unique properties allow for diagnosing and treating a wide range of diseases, revolutionizing healthcare and improving patient outcomes. This review explores the most commonly used radioisotopes, their characteristics, and their diverse applications in the diagnosis and treatment of different medical cases, highlighting the diagnostic techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) that have since revolutionized imaging by enabling detailed visualization of metabolic activities and anatomical structures. Furthermore, it highlights the therapeutic application of targeted radionuclide therapy (TRT), which leverages the precision of radioisotopes to deliver radiation directly to diseased cells, minimizing damage to healthy tissues. Finally, the challenges facing the use of radioisotopes are explored, along with the need for continued innovation and research to fully realize the potential of radioisotopes in healthcare.