Neighbourhood interventions are important for creating supportive structures for parents and children and for other community members. Little is known, however, about what works for whom in what situation. The aim of this study was to gain a better understanding of what works for whom in community interventions in the neighbourhood. Realist synthesis was used as a review methodology to examine community interventions. Six databases were searched for studies published between January 1st, 2000 and May 8th, 2020 and 28 community programs reported in 34 publications were included. Multiple rounds of coding and several discussions with experts and the project team were conducted to analyze these studies and programs, and to understand underlying assumptions of neighbourhood interventions. This resulted in the definition of ten important mechanisms of change in specific contexts. These were found on two levels: on an interpersonal level (e.g. social support) and on a community level (e.g. social norms). Positive mechanisms of change varied from supportive professionals to participants in the intervention, to co-production in developing the intervention. Negative mechanisms were only found on the community level and were related to professionals’ and community members’ skills. Mechanisms of change were found to be related to specific contexts, such as implementation strategies and the type of intervention. Professionals and municipalities can use these mechanisms of change to improve their interventions and neighbourhood practices.