Unhealthy eating and low levels of physical activity are major health risks, especially for older adults and people with a low socioeconomic status. The aim of this article is to describe the development of a community-based intervention aimed at promoting physical activity and healthy eating among people aged 55 years and over, in a socioeconomically disadvantaged community. The Intervention Mapping protocol was used to develop the intervention. We conducted a literature search, consultation with community partners and inhabitants, and a quantitative study, in order to obtain insight into the determinants of the target population and to identify appropriate theory-based methods and practical strategies for behavioural change. An assessment was performed of the problem with respect to health behaviour and the underlying determinants. Findings were translated into program, performance and change objectives which specify determinants related to behavioural change. Theory-based methods and practical applications were selected, resulting in a plan for adoption and implementation. The intervention included a local media campaign, social environmental approaches and physical environmental activities in the community, with an intermediating role for inhabitants and health professionals in the promotion of the campaign. An evaluation plan was produced to evaluate the effectiveness of the intervention. The Intervention Mapping protocol was a helpful instrument in developing a feasible, theory and evidence-based intervention tailored to a specific target population in the area of health promotion. The systematic and structured approach provided insight into the relationship between the objectives, methods and strategies used to develop the comprehensive intervention.