This book constitutes the proceedings of the First International Conference on Complex Computational Ecosystems, CCE 2023, held in Baku, Azerbaijan, during April 25-27, 2023. The 16 full papers and the 4 keynote abstracts included in this volume were carefully reviewed and selected from 46 submissions. They explore trans-disciplinary challenges that crossed theoretical questions with empirical observations of multi-level and multi-modal computational ecosystems.