The purpose of this study is to show that the analysis of activity is a factor in the construction of the collective self-efficacy of the trainers of five training institutes in nursing care (IFSI). As a collective system of beliefs about the capacity of the group to attain its goals, self-efficacy has its foundations in the sociocognitive theory, which articulates, within a mutual triadic causality, the personal, behavioral, and environmental factors of human agency. The personal determiners (self-efficacy, cognitive organization of activity) are connected to behavioral (production of the performance) and environmental (attribution of skill, professional tasks and standards) factors. The intervention consisted in introducing one hundred and nine nurse trainers to work analysis in a context of hospital reforms. The collective self-efficacy of the trainers appears to be a key variable in the success of these reforms. The collective self-efficacy was the object of a pre-test and a qualitative post-test based on motivational indicators of the effectiveness of the educational realizations to the students and the estimation of the performance of the group in conducting the reform. The level of collective self-efficacy increases, and the first results maintain trainers’ belief in their capacity to succeed collectively in the implementation of the training plan. This is the first study in France which shows that the analysis of the activity comes along with an increase in the collective self-efficacy in work. These results raise questions about the practices of trainers beyond the paramedical sector alone.