This book constitutes the refereed proceedings of the 12th International Conference on Computational Logistics, ICCL 2021, held in September 2021. Due to COVID-19 pandemic the conference was held virtually. The 42 full papers were carefully reviewed and selected from 111 submissions. They detail the interface of complex logistics systems and advanced computational methods from the fields of operations research, business analytics, and artificial intelligence. The papers are organized in topical sections named maritime and port logistics; supply chain and production management; urban transport and collaborative logistics; routing, dispatching, and scheduling; air logistics and multi-modal transport.