To the best of our knowledge, this study is the first to track and demonstrate the mortality event in Diadema setosum(Leske, 1778)along the Egyptian Red Sea coasts. The diadematid is a group of echinoid echinodermates that play an important ecological role in marine ecosystems. However, the current global mass mortality events in Diadema setosum have the potential to significantly change the fundamental structure of the ecosystem. This report was based on the 2023-summer observations of a D. setosum die-off during an ecological investigation in the northern Red Sea, Egypt. To determine the entirety of the event, a group from the Red Sea protectorates carried out an extensive survey simultaneously. The current survey covered the coastal regions of the Elba protectorate in the south, the Wadi El Gemal protected area in the middle, and Hurghada in the north. A diverse population of D. setosum was found dead on the bottom during both snorkeling and scuba diving. Representative photographs were taken at each explored site. Several features were noticed in the dead D. setosum, including a frail body, sand-covered body parts, spines distributed on the bottom, and inactive tube feet. The current findings, therefore, recommend crucially the performance of regular monitoring for the status of D. setosum. In addition, biological and ecological investigations are needed as soon as possible to interpret the causative and potential factors responsible for D. setosum loss.