This book constitutes the proceedings of the Third Decision Science Alliance International Summer Conference, DSA ISC 2025, held in Catania, Italy, in June 2025. The 25 full papers and 7 short papers were included in this book were carefully reviewed and selected from 70 submissions. This edition focused on Intelligent Systems and Decision Making: Human Insights in the Era of AI theme, with particular focus on the new frontiers of AI-driven Decision Making in academic and industrial research.