Thirty years after the Chernobyl nuclear accident, this article reviews the current epidemiological evidence regarding thyroid cancer. The incidence of this cancer has risen significantly over the past 30 years, both in France and worldwide. Improvements in diagnostic practices are considered the main explanation for this increase, and some authors even believe that this leads to significant overdiagnosis. Furthermore, exposure to ionizing radiation during childhood—whether external (X-rays or gamma rays) or internal (ingestion of iodine-131)—remains the primary known risk factor for this cancer today. The fallout from the Chernobyl nuclear accident has thus raised significant concerns in France and Europe, and increasing exposure to ionizing radiation from medical or dental sources is a cause for concern. Studies conducted on populations living near the Chernobyl power plant at the time of the accident have provided new insights into the epidemiology of this cancer, particularly regarding the impact of iodine-131 contamination during childhood. However, studies initiated following the Fukushima accident highlight the difficulties in estimating the impact of radioactive fallout from a nuclear accident on the incidence of thyroid cancer in the context of potential overdiagnosis. It is important to consider a strategy for collecting and generating information that would allow for estimating the actual public health impact of a nuclear accident, in the event of such an accident occurring in Europe.