This book constitutes the refereed proceedings of the 15th International Conference on Virtual, Augmented and Mixed Reality, VAMR 2023, held as part of the 25th International Conference, HCI International 2023, in Copenhagen, Denmark, in July 2023. The total of 1578 papers and 396 posters included in the HCII 2022 proceedings was carefully reviewed and selected from 7472 submissions. The VAMR 2023 proceedings were organized in the following topical sections: Designing VAMR Applications and Environments; Visualization, Image Rendering and 3D in VAMR; Multimodal Interaction in VAMR; Robots and Avatars in Virtual and Augmented Reality; VAMR in Medicine and Health; VAMR in Aviation; and User Experience in VAMR.