Introduction: The description of the contents and underlying theoretical principles of a behaviour change intervention is a fundamental step to allow the reproduction of success factors of effective interventions. The objective of this article is to describe the scientifically-based construction of a multimodal media campaign implemented by the National institute for prevention and health education to promote physical activity and more particularly walking among physically inactive women.Methods: The first five stages of this intervention are described. They include definition of the objectives, identification of target populations, the behaviour change theories used, identification of the effective behaviour change techniques and the modes of delivery of the campaign.Results: The main objective of the media campaign is to encourage inactive women to walk by means of a mass media campaign and a mobile application. It also targets the general population by the development of a specific section about physical activity on the mangerbougerfr website. It is based on the COM-B system- a framework for understanding behaviour, on the theory of planned behaviour and on effective behaviour change techniques.Conclusion: This paper demonstrates the feasibility of developing a multimodal media campaign-based intervention to promote physical activity using theory, evidence and media campaign construction expertise. An evaluation of this media campaign and its various components is the next stage of this work.