The commitment to church membership in Germany depends on two major aspects, the overall societal discourse about the church and the very concrete experiences with the local church community. While the societal discourse is transmitted via public media, it is not so clear which factors form the opinion and bond towards the church communities on the local level. For congregations it is crucial, to identify activities and communications that support and lead to sustained membership. In a mixed-methods study in the German Roman Catholic diocese of Speyer, we examined the connection between actions and practices of parishes and their impact on membership in three steps. First, we analysed church statistics to rank all local church communities based on their success in maintain/increasing church membership; second, we identified five particularly successful congregations, characterised by high levels of commitment, and conducted a qualitative field study to see, which characteristics of their actions could explain their success. Six central attributes were identified: Building relations, facilitate participation, empower youth, ensure contextuality, live catholic identity. Third, these attributes were operationalised in terms of their measurability. The data was collected using a standardised questionnaire among all church communities in the diocese to test the correlation between the success in maintaining/increasing church membership and action attributes. The results show that, secularization is a societal trend in Germany, but church membership also is affected by the actions and possibilities in the local communities. The results will be discussed in the context of studies on congregations of other religious affiliations, like the Congregational Studies (Kirchengemeindebarometer), which examined protestant congregations in different countries.