This book constitutes the  post proceedings of the 18th International Workshop on Security and Trust Management, STM 2022, co-located with the 27th European Symposium on Research in Computer Security, ESORICS 2022, which took place in Copenhagen, Denmark, in September 2022. The 7 full papers together with 4 short papers included in this volume were carefully reviewed and selected from 18 submissions. The workshop presents papers with topics such as security and trust access control, cryptographic protocols, identity management, security metrics, and privacy.