This study aims to provide framework for considering fidelity in the design of simulator training. Simulator fidelity is often characterised as the level of physical and visual similarity with real work settings, and the importance of simulator fidelity in the creation of learning activities has been extensively debated. Based on a selected literature review and fieldwork on ship simulator training, this study provides a conceptual framework for fidelity requirements in simulator training. This framework is applied to an empirical example from a case of ship simulator training. The study identifies three types of simulator fidelity that might be useful from a trainer’s perspective. By introducing a framework of technical, psychological and interactional fidelity and linking these concepts to different levels of training and targeted learning outcomes, the study demonstrates how the fidelity of the simulation relates to the level of expertise targeted in training. The framework adds to the body of knowledge on simulator training by providing guidelines for the different ways in which simulators can increase professional expertise, without separating the learning activity from cooperative work performance.