This book constitutes the refereed proceedings of the 18th International Conference on Formal Modeling and Analysis of Timed Systems, FORMATS 2020, held in Vienna, Austria, in September 2020. The 16 full papers and 2 short papers presented in this volume were carefully reviewed and selected from 42 submissions. The papers focus on topics such as foundations and semantics, methods and tools, techniques, algorithms, data structures, and software tools for analyzing timed systems and resolving temporal constraints. Due to the Corona pandemic this conference was held as a virtual event.