This book constitutes the proceedings of the 21st International Conference on Cooperative Design, Visualization, and Engineering, CDVE 2024, held in Valencia, Spain, in September 2024. The 34 full papers and 5 short papers presented were carefully reviewed and selected from 74 submissions. The papers cover a wide application spectrum including AI technology, cooperative engineering, basic technologies for cooperative applications, IOT internet of things, block chain technology, sensor networks, and more.