This book constitutes the proceedings of the 18th International Conference on Software and Systems Reuse, ICSR 2019, held in Cincinnati, Ohio, USA in June 2019. The 13 research papers included in this book were carefully reviewed and selected from 32 submissions. In addition, 3 industry innovation papers are included. The papers were organized in topical sections named: software reuse practice; software product line and requirements reuse; reuse and design and evolution; intelligent software reuse; and domain-specific software development.