This book constitutes the refereed proceedings of the 5th European Conference on Software Architecture, ECSA 2011, held in Essen, Germany, in September 2011. The 13 revised full papers presented together with 24 emerging research papers, and 7 research challenge poster papers were carefully reviewed and selected from over 100 submissions. The papers are organized in topical sections on requirements and software architectures; software architecture, components, and compositions; quality attributes and software architectures; software product line architectures; architectural models, patterns and styles; short papers; process and management of architectural decisions; software architecture run-time aspects; ADLs and metamodels; and services and software architectures.