Nuclear-powered pacemakers were implanted in the 1970s. At that time, there was a strong need to overcome the limitations of available batteries. Nickel-cadmium batteries used at the very beginning of cardiac pacing had a very short life and therefore needed to be charged up on a regular basis. Later on, the lifespan of mercury-zinc batteries that were widely used in the late 1960s was also short, approximately 18 months, and unpredictable. With a half-life of 87.7 years, the radioactive isotope of plutonium (²³⁸Pu) appeared as an attractive alternative for powering pacemaker batteries. The last implantations of these devices took place in the late 1980s, when they were put out of fashion by the introduction of lithium-powered batteries combined with the sophistication of pulse generators (Fig. 1). Nowadays, few patients are still alive with such devices, and their management may be challenging. We report the case of a patient who was successfully paced by a nuclear-powered pacemaker (plutonium-238 radioisotope) for 35 years. This is the longest life of a nuclear-powered pacemaker ever reported. Due to the potential risk of device malfunction in this patient with complete atrioventricular block, it was decided to fit the patient with a “modern” pre-pectoral pacemaker (lithium-powered battery and endocardial leads). Loss of ventricular capture from the nuclear-powered pacemaker did occur after 35 years of reliable service, and pacing was subsequently performed by the “modern” pre-pectoral pacemaker. This short report emphasizes the need for implanting modern pacemakers in the small number of patients worldwide that are still paced with nuclear-powered pacemakers, as the battery expiration date cannot be reliably predicted. Nowadays, ²³⁸Pu is mostly used by NASA, in radioisotope thermoelectric generators that provide energy for spacecrafts.