The aim of this special collection is twofold: (1) to assess the legacy of Dennis S. Mileti’s contributions to risk communication research and (2) to explore and advance the future of public alert and warning research, policy, and practice globally. Dr. Mileti was regarded by many of his colleagues as the world’s foremost expert on public alert and warning research. Tragically, he died from complications due to COVID-19 in 2021. An esteemed disaster sociologist and former Director of the Natural Hazards Center at the University of Colorado Boulder, Dr. Mileti’s influence on the fields of public alert and warning, sustainable hazards mitigation, and human behavior during emergencies is difficult to overstate: It can be seen in the 100+ publications he authored or co-authored over the course of his 50-year career, the thousands of scholarly citations of his work, the engagement of countless practitioners and students he taught or trained, and the public alert and warning policies and practices that his research influenced worldwide. Amid the lingering pandemic, intensifying effects of climate change, and accelerating technological transformations, there is urgent need to take stock of Dr. Mileti’s contributions to public alert and warning practice and chart a future path that both honors his legacy and builds upon his pioneering research.