Networks are increasingly used in public policy to tackle ever more complex societal challenges. Multi-stakeholder governance systems have been set up to strengthen regional innovation systems, to fight the consequences of climate change and to tackle social change. However, multiple challenges mean that evaluating these networks and governance systems is complex and requires specific evaluation approaches. Learning from the strengths and weaknesses of existing approaches, this article presents a new tool (GOCAPASS) which enables evaluators to assess governance systems and networks involving multiple stakeholders. It has already been tested in regional innovation policy and governance of EU macro-regional strategies. Practical testing demonstrated its usefulness as a tool for evaluation and policy learning, though some weaknesses still need to be resolved.