This book constitutes the refereed proceedings of the 9th International Conference on Web Engineering, ICWE 2009, held in San Sebastian, Spain in June 2009. The 22 revised full papers and 15 revised short papers presented together with 8 posters and 10 demonstration papers were carefully reviewed and selected from 90 submissions. The papers are organized in topical sections on accessibility and usability, component-based web engineering: portals and mashups, data and semantics, model-driven web engineering, navigation, process, planning and phases, quality, rich internet applications, search, testing, web services, SOA and REST, and web 2.0.