Human-centred design (HCD) is a form of open innovation in which researchers and designers cooperate with (potential) users or customers, e.g. in co-design workshops, interviews, user tests and trials. Based on a case study of two open innovation projects in which HCD activities were organized (TA2 and WeCare), and a survey amongst team members of these projects, we furthered our understanding of the practical benefits, costs and risks of organizing HCD in such projects. We found benefits for idea generation and service development, and also benefits for project management, for the participating organization(s) and for the longer term. We also provide several tentative recommendations for managers and team members of such projects to organize HCD effectively, so that they can practically realize these benefits and develop products or services that match people's needs and preferences.