This book constitutes the refereed proceedings of the 4th International Conference on Design, Operation and Evaluation of Mobile Communications, MOBILE 2023, held as part of the 25th International Conference, HCI International 2023, which was held in Copenhagen, Denmark, during July 23-28, 2022. The total of 1578 papers and 396 posters included in the HCII 2022 proceedings was carefully reviewed and selected from 7472 submissions. The MOBILE 2023 proceedings were organized in the following topical sections: Mobile User Experience and Interaction Design; Design and Evaluation of Voice User Interfaces and Conversational AI; and Mobile Information Systems in Education, Healthcare, eCommerce and Beyond.