Evolutionary multi criterion optimization : 12th International Conference EMO 2023 Leiden The Netherlands March 20 24 2023 : proceedings This book constitutes the refereed proceedings of the 12th International Conference on Evolutionary Multi Criterion Optimization EMO 2022 held in Leiden The Netherlands during March 20 24 2023.The 44 regular papers presented in this book were carefully reviewed and selected from 65 submissions.The papers are divided into the following topical sections: Algorithm Design and Engineering; Machine Learning and Multi criterion Optimization; Benchmarking and Performance Assessment; Indicator Design and Complexity Analysis; Applications in Real World Domains; and Multi Criteria Decision Making and Interactive Algorithms