Reflexivity is a key expectation that researchers in transdisciplinary and transformative research for sustainable development need to meet. Its aim is to enable researchers to deal with normativity, to contribute to identifying and balancing different actors’ interests in processes of knowledge production, and to strengthen a pluralistic view of implicit assumptions. When designing and realizing transdisciplinary and transformative studies, researchers face a central question: How can we develop reflexive practices and live up to the demands of such work? Considering the important role that reflexivity plays in transdisciplinary approaches, it is surprising that only few approaches have explored the specific characteristics of reflexive practices empirically and analyzed how these practices are cultivated when doing transdisciplinary and transformative research. In this article we address this research gap by presenting and discussing a case in which researchers attempted to professionalize their reflexive practices at the science-policy interface (SPI). As part of the national Monitoring of Education for Sustainable Development in Germany, we used the method of collaborative autoethnography to systematically reflect on our own thinking and actions as researchers at the SPI over a period of 11 months. Based on an analysis of 66 situations in which we took field notes, we synthesized core topics of reflection and challenges encountered throughout the process (roles, relationship patterns, and normativity) in six collaborative interpretation sessions and analyzed them to understand our own practices of engagement within the field. Grounded in this analysis of our own selves as researchers looking in the mirror, we develop hypotheses about how our specific methodological approach helped us on a practical level to foster different kinds of reflexivity. With this two-fold approach, we aim to contribute to a better understanding of possible topics, challenges, and pathways of (increased) reflexivity among researchers working at the SPI.