Inhalt: The Women Professors Program, which was initiated in Germany in 2008, aims to increase the proportion of women professors and to promote structural change in favour of gender equality at higher education institutions (HEIs). It is one of the central gender equality policies in higher education in Germany. The present study evaluates the impact of the program by estimating its causal effects on the proportion of women professors. By adopting a quasi-experimental approach and using a unique dataset—a long term census of German HEIs—the study proves that the proportion of women professors increased more than would have been expected in the absence of the program. Although the evaluation includes preliminary estimates of mechanisms driving the described impacts, the integration of context factors and mechanisms into the assessment of the impact of gender equality policies remains a desideratum. The study shows that the program is working, and it contributes to redressing the lack of impact studies on gender equality in science and research.