This book constitutes the proceedings of the 12th International Symposium on Advanced Parallel Processing Technologies, APPT 2017, held in Santiago de Compostela, Spain, in August 2017.The 11 regular papers presented in this volume were carefully reviewed and selected from 18 submissions. They deal with the recent advances in big data processing; parallel architectures and systems; parallel software; parallel algorithms and artificial intelligence applications; and distributed and cloud computing.