The potential of serious games is in their ability to facilitate engaging learning experiences for the user. This paper describes a serious game that has been designed using a framework that aligns instructional objectives with core-gameplay. Catastrophe, the Occupational Health and Safety game developed for this project, has been evaluated to determine the extent to which it promotes both engagement and learning. In comparison to e-Learning methods, the game produces significantly better learning outcomes and significantly higher levels of intrinsic motivation. The quantitative and qualitative results of this study are reported and discussed.