Population aging and urbanization are often associated with a restriction of the living environment and an increasing tendency to remain at home. This community development report presents the "Neighborhood in Solidarity" methodology as a response to counter or at least slow this restriction and enhance the ability of elderly persons to be active within their neighborhoods. Co-constructed throughout the action research process, the Neighborhood in Solidarity methodology is based on a 13-year experience, accumulated through 22 projects in 17 cities, with promising results in the Canton of Vaud in Switzerland. The genesis and the emergence of the methodology throughout action research workshops and interregional structures are described in the document. The description of Neighborhood in Solidarity is a snapshot of a living methodology, which continues to evolve on a daily basis. The process focuses on empowering the older people through a five-year methodology, which is intended to create an autonomous community that can resolve its own problems. The methodology comprises six steps described throughout the paper: (1) preliminary analysis, (2) diagnostic, (3) construction, (4) project design, (5) project implementation, and (6) empowerment. In 2013, an external assessment evaluated the Neighborhood in Solidarity methodology as effective at and appropriate for achieving its objectives. The promising results of this original methodology motivated this publication.