This two-volume set constitutes the proceedings of the 11th International Symposium on Integrated Uncertainty in Knowledge Modelling and Decision Making, IUKM 2025, held in Ho Chi Minh City, Vietnam, during March 17-19, 2025. The 55 full papers in this book were carefully reviewed and selected from 116 submissions. They were organized in topical sections as follows: Part I: Invited Talks; Machine Learning; Pattern Recognition and Data Analysis; Applications. Part II: Uncertainty Management and Decision Making; Optimization and Statistical Methods; Applications.