This proceedings constitutes the post-conference proceedings of the 19th International Conference on Security and Privacy in Communication Networks, SecureComm 2023, held in October 2023 in Hong Kong, China. The 50 full papers were carefully reviewed and selected from 180 submissions. The papers are clustered in thematical issues as follows: AI for Security; Authentication; Blockchain and Distributed System Security; Cryptography; Data Security; Intrusion and Anomaly Detection; IoT Security; Network Security; Privacy; Program Analysis; Software Security.