This book constitutes the refereed proceedings of the 18th International Conference on Verification and Evaluation of Computer and Communication Systems, VECoS 2025, held in Paris, France, during November 5-7, 2025.The 13 full papers included in this book were carefully reviewed and selected from 29 submissions. They focus on state of the art research and challenges in verification, control, performance, and dependability evaluation for modern computer and communication systems.