The participation of citizens in scientific research has a long tradition, and in some disciplines, especially medical research, it is even common practice. In Technology Assessment (TA), Responsible Research and Innovation (RRI), and Sustainable Development (SD), the participation of citizens can be of considerable value. In this paper, we explore this value for three concepts, based on the researcher’s insights from three participatory research projects. The first project is the citizen science project TeQfor1, which was conducted with, for, and on the type 1 diabetes community, who do not feel adequately supported by the conventional health care system. In the second project, citizens with vision impairments participated in the technological development of an audio-tactile navigation tool in the TERRAIN project. The third project (Nachtlichter) dealt with light pollution. Based on the three projects presented, we show that citizen participation makes specific contributions to TA, RRI, and SD. We also investigate the specificity of citizen engagement and motivation by differentiating between existing and emerging involvement. In conclusion, we discuss the benefits that may be added by participatory approaches for the three concepts of TA, RRI, and SD.