This volume constitutes the proceedings of 31st International Conference on Cooperative Information Systems, CoopIS 2025, held in Marbella, Spain, during October 20–22, 2025. The 24 full papers and 21 short papers included in this book were carefully reviewed and selected from 128 submissions. They were organized in topical sections as follows: Invited Speakers; Data-Driven and Predictive Process Analytics; Neuro-Symbolic Systems and Knowledge Graphs; Process Conformance, Integrity and Compliance; Intelligent and Secure Connected Systems; Process Discovery and Variability; Architecture Engineering and Governance of Information Systems; and Short Papers.