This book constitutes the refereed proceedings of the 18th EAI International Conference on Performance Evaluation Methodologies and Tools, Valuetools 2025, which took place in Glasgow, UK during December 11–12, 2025The 18 full papers presented in this volume were carefully reviewed and selected from 46 submissions. They were organized into topical sections as follows: Queueing Models; Stochastic Models; Cyber Attacks; Tools; Networks and Routing.