This book constitutes the proceedings of the 6th International IFIP Working Conference on Enterprise Interoperability, IWEI 2015, held in Nimes, France, in May 2015. The event was organized by the IFIP Working Group 5.8 on Enterprise Interoperability in co-operation with INTEROP-VLab and PGSO (Pole Grand Sud Ouest) from INTEROP-Vlab. The theme for IWEI 2015 was "From Enterprise Interoperability Modelling and Analysis to Enterprise Interoperability Engineering." The nine full, four short, and two industrial papers presented in this volume were carefully selected from 20 submissions. The selection was based on a thorough review process, in which each paper was reviewed by at least three experts in the field. The papers are representative of the current research activities in the area of enterprise interoperability. They cover a wide spectrum of enterprise interoperability issues, including foundational theories, frameworks, architectures, methods and guidelines, and applications and case studies.