The paper focuses on how to evaluate impact of an organisation in a complex environment. We present the results and lessons learned from the wide-scale evaluations of the public future-oriented organisation Sitra. Sitra’s mission is to build a successful Finland of tomorrow, and its work is guided by the vision of a fair and sustainable future. Due to its strategy, Sitra takes on complex and multifaceted problems. The paper presents Sitra’s approach to impact evaluation that is guided by the nature of its operations and the need for knowledge that supports work aimed at generating systemic changes. Based on the evaluations carried out in 2016-2019, we reflect, from the viewpoint of evaluation management, the value of the systemic evaluation approach and the knowledge it has produced. We bring forth what kind of new mindsets, capacities and collaboration this kind of evaluation requires from the organisation, independent evaluators and evaluation users.