“Citizen Social Science” is a fast-growing term within Citizen Science world but not many experiences have been shared in the literature to better shape its meaning. This article discusses novel possibilities of these participatory practices through the critical analysis of a concrete community-based project. We here embrace under the “Social” tag of Citizen Social Science both Computational Social Science methodologies and the Social concerns expressed by the mental health community. The interpretation place persons with a mental condition, as well as caregivers and relatives, at the center of the research cycle by taking the role of Competent Experts In-The-Field. A synergetic relation between Citizen Science, Mental Health research and Computational Social Science also imply a conceptual shift in comparison to standard approaches such as the inclusion of research subjects as active co-designers or the consideration of communitarian spaces as most natural experimental spaces. We here describe how these concepts are put into practice during the whole duration of a research project that has studied the social interactions inside the Community Mental Health Care ecosystem. Important steps entail the creation of a Knowledge Coalition, including a diversity of relevant actors with diverse knowledge and expertise, that is later involved in co-designing the research and in embedding experimental settings in communitarian spaces. The experience allows us to open a wider discussion on the possibilities and limitations of Citizen Social Science practices. Having in mind the ethical debate raised by Citizen Science Public Health and Patients’ driven research, we propose a set of values and practices to be agreed on. We also analyse the participation of the scientists in these kind of projects, which forces them to adopt the role of “camaleons” when executing diverse and versatile tasks. We additionally advocate for a more extended collective interpretation of the results in order to produce socially robust knowledge and enhance actions and policies grounded on these results. Exemplified with the experience herein presented, a more horizontal process that include the enhancement of participation and the revision of the notion of experiment offer new opportunities for Social Sciences from a multidisciplinary perspective.