This book constitutes the proceedings of the 15th International Conference on Parallel Computing Technologies, PaCT 2019, held in Almaty, Kazakhstan, in August 2019. The 24 full papers and 10 short papers presented were carefully reviewed and selected from 72 submissions. The papers are organized in topical sections on Programming Languages and Execution Environments, Methods and Tools for Parallel Solution of Large-Scale Problems, Data Processing, Cellular Automata, and Distributed Algorithms.