In theory-based evaluations, program theories are used to illustrate and to analyze how program activities bring about outcomes. However, in order to gain a holistic understanding of a program, it is important to also consider the orientation and motivation of involved actors. In a research project, funded by the Austrian Central Bank’s Anniversary Fund, system constellations – a tool applied in systemic consultation practice – were for the first time tested in the context of theory-based evaluations. System constellations were applied as a heuristic tool to rapidly give an insight into formal and informal relations between program actors. The insights gained during constellations work can offer a basis for more actor-centred program theories and evaluations. Program actor constellations facilitate the drafting of program theories and allow for more accurate statements about intended and unintended effects. Furthermore, they can be used as a basis for evaluation designs and as a creative research and communication tool. The article uses a case study to illustrate and reflect upon the initial experiences made with system constellations in theory-based evaluations.