This book constitutes the refereed proceedings of the 15th International Conference on Pattern Recognition and Information Processing, PRIP 2021, held in Minsk, Belarus, in September 2021. Due to the COVID-19 pandemic the conference was held online. The 17 revised full papers were carefully reviewed and selected from 90 submissions. The papers present a discussion on theoretical and applied aspects of computer vision, recognition of signals and images, the use of distributed resources, and high-performance systems.