This book constitutes the proceedings of the 15th International Conference on Intelligent Virtual Agents, IVA 2015, held in Delft, The Netherlands, in August 2015. The 11 full papers, 22 short papers, and 21 demo and poster papers accepted were carefully reviewed and selected from 70 submissions. Constructing and studying intelligent virtual agents requires knowledge, theories, methods, and tools from a wide range of fields such as computer science, psychology, cognitive sciences, communication, linguistics, interactive media, human-computer interaction, and artificial intelligence. The...