This book constitutes the refereed proceedings of the 35th International Conference on Conceptual Modeling, ER 2017, held in Valencia, Spain, in November 2017. The 28 full and 10 short papers presented together with 1 full 6 keynotes were carefully reviewed and selected from 153 submissions.This events covers a wide range of following topics: Conceptual Modeling Methodology, Conceptual Modeling and Requirements, Foundations, Conceptual Modeling in Specifi c Context, Conceptual Modeling and Business Processes, Model Efficiency, and Ontologies.