This book constitutes the refereed proceedings of the 31th International Colloquium on Structural Information and Communication Complexity, SIROCCO 2024, held in Haifa, Israel in May 2024. The 24 full papers and 6 short papers presented in this book were carefully reviewed and selected from 49 submissions. SIROCCO is devoted to the study of the interplay between structural knowledge, communication, and computing in decentralized systems of multiple communicating entities. Special emphasis is given to innovative approaches leading to better understanding of the relationship between computing and communication.