In The Netherlands there is an increasing drive for social sustainable (developer-led) development. This is reflected in the upcoming ‘Omgevingswet’ (spatial planning law) due for 2022, that will require participation to be an (significant) element (in the early phases) of the urban development project. Existing research focuses mainly on the effects of participation on the residents, linking it to social sustainability. However, there is a lack of research into the effects of participation on urban redevelopment projects for the developer. Currently, the (positive) effects and implementation of participation within processes of developers are mainly based on ‘gut feelings’. Therefore, the main research question answered in this thesis is: What are the effects of participation on Dutch urban (re)development projects for the developer? The aim of this thesis is to provide insight, based on theoretical and empirical research, into the effects of the voice and influence (participation) of residents on urban (re)development projects, for the developer. The research has two key components: a case study and an inductive analysis, on the effects of participation on urban development projects. In the case study two cases from the Dutch developer ERA-Contour are analysed, on how the participation process affected the GOTIK aspects and the change in social cohesion of the neighbourhood. The inductive analysis of the findings is used to determine and present practical advice to urban developers on participation in urban redevelopment projects. The case study shows that participation enhances the quality and social cohesion of urban (re)development projects, it also contributes to the certainty about decisions made during the project and the level of support by residents for the project. To achieve these effects, participation requires the investment of time and money and a change in the approach to the organisation and information aspects of an urban (re)development project. Practical advice for the implementation of participation is provided. The lessons learned from this research can be applied to future urban development projects. This knowledge can help developers, to effectively use participation with residents and create more social sustainable neighbourhoods.