The objective of this study is to compare the interventionist methodologies of Ergonomic Work Analysis (EWA) influenced by a French approach, and the Change Laboratory method based on the Activity Theory approach. This study aims at identifying complementarities and convergences between these methods to improve work related accident and diseases prevention. Reference publications of these two methodologies were selected to make a theoretical comparison between the approaches. The criteria selected for the comparison were: units of analysis and key concepts, main methodological principles, the role of demand, main steps of the method, the relationship between the diagnosis and creation and construction of new solutions processes, the role of researcher / interventionist, the role of practitioners and ethical issues. Based on this comparison, resources will be drawn from both approaches to map out the ingredients for efficient intervention for the prevention of accidents and health problems related to work. We argue that ergonomic analysis has as its main strength deep and detailed understanding of the actions and operations of workers engaged in real work, while, on the other hand, the Change Laboratory seeks understanding within a historical and systemic perspective and emphasizes intervention in the whole activity system.