This book constitutes the refereed proceedings of the 19th European Conference on Software Architecture, ECSA 2025, held in Limassol, Cyprus, during September 15–19, 2025. The 18 full papers and 9 short papers presented in this volume were carefully reviewed and selected from 80 submissions. They are grouped into the following topics: Architectures for MLOps; Large Language Models in Software Architecture; Architectures for Embedded Systems; Self-Adaptive, Secure and Federated Learning Systems; Microservice Architecture; Software Architecture Practices, Perspectives and Evolution; Industry papers.