Managing boundaries is at the heart of spatial governance. It happens when forms of land use are distinguished, when differences between groups need to be bridged in deliberations, and when governments share responsibility with non-governmental actors. In all these situations, boundaries – physical/spatial, social or institutional – are defined, bridged or shifted. I aim to apply theory on boundary management to the field of spatial governance by analysing cases in agri-environmental management and urban regional planning in the Netherlands. This is relevant because of the broader shift in society toward more responsibility for societal actors – citizens, civil society and firms. It is also relevant because of the increasingly complex nature of spatial governance, not in the least because of scarce resources and declining biodiversity, leading to claims on and challenges for the use of space. The main research question is: How do boundary arrangements in spatial governance function? The thesis is built on published and prepared work, which is analysed again from the perspective of boundary management.