This book constitutes the refereed post-conference proceedings of the 17th International Conference on Advances in Computer Games, ACG 2021, which was held as a virtual event during November 23-25, 2021. The 22 full papers included in this book were carefully reviewed and selected from 34 submissions. They were organized in topical sections as follows: learning in games; search in games; solving games; chess patterns; player modelling; and game systems.