When considering how ethical considerations should be applied to the practice of spatial planning, most attention has been given to how individual spatial planners should do that. Our focus in this article is different: it is on the public agencies that carry out spatial planning. What ethical principles should they follow, both for determining the content of the planning policy and the procedures by which those principles are applied? We argue that it is possible to construct a ‘domain ethics’ specifically for spatial planning, a set of normative principles based on widely shared values and taking account of the peculiar features of spatial planning. Using four sources — some ‘middle‐range’ ethical principles, national law, international law, and the principles behind the idea of ‘due process’— a domain ethics for spatial planning is put forward. In the ‘power game’ of planning practice, the public agency should adhere to these ethical principles. Ultimately, this is a task for the individual planner acting responsibly within the organization. We argue that planners should construct an ethical frame of reference, specifically adapted to every situation, which takes into account the nature and motivations of the other partners in that power game. That frame of reference should be established before the discussions and negotiations begin, and it should be used to influence them.