This book constitutes the refereed proceedings of the 15th International Conference on Decision and Game Theory for Security, GameSec 2024, which took place in New York City, USA, in October 2024. The 15 full papers included in this book were carefully reviewed and selected from 27 submissions. They were organized in topical sections as follows: systems security; economics; equilibrium and control; cyber deception; network and privacy; adversarial machine learning; and cyber-physical systems.