This book constitutes the refereed proceedings of the 20th International Symposium on Automated Technology for Verification and Analysis, ATVA 2022, held in Beiging, China in October 2022. The symposium is dedicated to promoting research in theoretical and practical aspects of automated analysis, verification and synthesis by providing an international venue for the researchers to present new results. The 21 regular papers presented together with 5 tool papers and 1 invited paper were carefully reviewed and selected from 81 submissions. The papers are divided into the following topical sub-headings: reinforcement learning; program analysis and verification; smt and verification; automata and applications; active learning; probabilistic and stochastic systems; synthesis and repair; and verification of neural networks.