This book constitutes the refereed proceedings of the 14th International Conference on Software Architecture, ECSA 2020, held in A'quila, Italy, in September 2020. In the Research Track, 12 full papers presented together with 5 short papers were carefully reviewed and selected from 103 submissions. They are organized in topical sections as follows: microservices; uncertainty, self-adaptive, and open systems; model-based approaches; performance and security engineering; architectural smells and source code analysis; education and training; experiences and learnings from industrial case studies; and architecting contemporary distributed systems. In the Industrial Track, 11 submissions were received and 6 were accepted to form part of these proceedings. In addition the book contains 3 keynote talks. Due to the Corona pandemic ECSA 2020 was held as an virtual event.