This book constitutes the refereed proceedings of the 28th International Conference on Conceptual Modeling, ER 2009, held in Gramado, Brazil, in November 2009. The 31 revised full papers presented together with 18 demo papers were carefully reviewed and selected from 162 submissions. The papers are organized in topical sections on conceptual modeling, requirements engineering, query approaches, space and time modeling, schema matching and integration, application contexts, process and service modeling, and industrial session.