This report and the accompanying presentation describe the work and impact of the Open Science Office of the University of Mannheim since its establishment in 2021 until autumn 2023. It provides details on the following evaluation dimensions: Open Science Training and Education, Open Science Consulting and Funding, and Networking and Visibility. Based on this report, the Open Science Council and ultimately the President’s Office of the University of Mannheim later decided to make the Open Science Office permanent. This impact report can also serve as a useful tool for other research institutions wishing to embed Open Science at an institutional level. It also provides important insights into how researchers can be supported with open, transparent, and reproducible research practices.