The aim of this paper is to identify what kinds of ethical issues practitioners have to consider in participatory design practice and use these to inform a set of ethical principles which can be used to guide practice. It begins by discussing the ways in which participatory design as a discipline has engaged with ethical issues in the past and looks at how other disciplines have identified ethical principles to support ethical practice. It then draws upon interviews with researchers who have experience of collaborative and participatory design projects in order to identify ethical considerations that they have encountered in their work and uses these to propose a set of ethical principles. Finally, it ends with a discussion about how a principles approach can be combined with other approaches, such as the cultivation of virtues, in order to support ethical practice in Participatory Design.