An extensive knowledge of a system’s failures is crucial for identifying areas where the reliability of the system can benefit from improvements, as well as informing the design of new systems. Moreover, relationships between faults and failures can be used to enhance the maintenance of the system. In this paper we present a taxonomy of failure modes of the JET Remote Handling System. This system is used during maintenance and enhancements of in-vessel systems, and consists of two transporters (booms) and a two-armed manipulator, along with a number of supporting systems. In this work we first present a failure taxonomy suitable for our specific system, and then we apply this taxonomy model to our failure database. The presented failures have been collected during commissioning and operations over a period of over 5 years. Cataloged failures are extracted from the logs produced by the control system and from the daily log books recorded by the system operator.