This book presents selected, peer-reviewed contributions from the 9th International Conference on Experimental Vibration Analysis for Civil Engineering Structures (EVACES 2021), organized by the University of Tokyo and Saitama University from September 17-20, 2021 on the Hongo campus of the University of Tokyo, and hosted in an online format. The event brought together engineers, scientists, researchers, and practitioners, providing a forum for discussing and disseminating the latest developments and achievements in all major aspects of dynamic testing for civil engineering structures, including instrumentation, sources of excitation, data analysis, system identification, monitoring and condition assessment, in-situ and laboratory experiments, codes and standards, and vibration mitigation. The topics of EVACES 2021 included but were not limited to: damage identification and structural health monitoring; testing, sensing and modeling; vibration isolation and control; system and model identification; coupled dynamical systems (including human-structure, vehicle-structure, and soil-structure interaction); and application of advanced techniques involving the Internet of Things, robot, UAV, big data and artificial intelligence.