This book constitutes the refereed post proceedings of the 19th International Conference on Advances in Computer Games, ACG 2025, held online, during October 21&23, 2025 . The 17 full papers included in this book were carefully reviewed and selected from 30 submissions. They were organized in topical sections as follows: Game Solvers, Engagement and Fairness, Large Language Models, Learning and Tree Search, Human Gameplay, Imperfect Information Games.