This book constitutes the refereed proceedings of the 18th International Conference on Virtual Reality and Mixed Reality, EuroXR 2021, held in Valencia, Spain, in November 2021. The 8 full and 4 short papers were carefully reviewed and selected from 31 submissions. The conference presents contributions on virtual reality, mixed reality, augmented reality, collaborative virtual environment, tangible user interface, CAD model processing, and others. The papers are organized in the blocks named: Perception and Cognition; Interactive Techniques; Tracking and Rendering; Use case and User study; Short papers.