This book constitutes the refereed proceedings of the 12th International Conference on Future Data and Security Engineering, FDSE 2025, held in Ho Chi Minh City, Vietnam, during November 27-29, 2025.

The 56 full papers and 10 short papers presented in these two volumes were carefully reviewed and selected from 215 submissions.

The papers are organized in the following topical sections:

Part I: Invited Keynote; Advances in Machine Learning for Big Data Analytics; Security and Privacy Engineering; Query Processing and Optimization; Data Analytics and Healthcare Systems; Smart City and Industry 4.0 Applications.

Part II: Invited Keynote; Advances in Machine Learning for Big Data Analytics; Security and Privacy Engineering; Query Processing and Optimization; Data Analytics and Healthcare Systems; Smart City and Industry 4.0 Applications; Short Papers: Security and Data Engineering.