Universities can contribute to the solutions of major challenges of the 21st century such as increasing environmental and socio-economic crises, inequalities of income and wealth and political instabilities by integrating the concept of sustainable development (SD) in research, organization, and by educating future decision makers. For instance, by integrating sustainability into the organization, universities can lead by example. Furthermore, through the curriculum, future decision makers can learn the competences needed to solve ecological, social, and economic problems in societies. However, despite their possible importance, universities in Germany fall behind internationally in implementing sustainable strategies. Therefore this paper presents/introduces an approach to how universities can implement the holistic concept of SD that considers all three dimensions (economic, ecological, and social) relating to their main functions of research and education in addition to their organization. Additionally this paper analyzes the current state of implementing sustainability strategies at universities, and how the success of these implementation efforts can be evaluated and be fostered further. We find that assessment systems enable universities to systematically use their potential for action for SD by initiating, evaluating, and accelerating the sustainability process. This also applies in the case of German universities, where the implementation of SD is still in the early stages.