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.

​Learning in Games.- Improving Counterfactual Regret Minimization Agents Training in the Card Game Cheat.- Deep Reinforcement Learning for Morpion Solitaire.- Expert Iteration for Risk.- Search in Games.- Sequential Halving Using Scores.- Cosine Annealing, Mixnet and Swish Activation for Computer Go.- A Heuristic Approach to the Game of Sylver Coinage.- Evaluating Interpretability Methods for DNNs in Game-Playing Agents.- Solving Games.- Quixo is Solved.- Solving Bicoloring-Graph Games on Rectangular Boards – Part 1: Partisan Col and Snort.- Solving Bicoloring-Graph Games on Rectangular Boards – Part 2: Impartial Col and Snort.- BoxOff is NP-Complete.