Educational Escape Rooms (EER) as a new teaching tool gained significant attention in the research discourse – especially the last two years. So far, research focused on the practicality, feasibility or description of the development. To provide a more comprehensive understanding to mechanisms within this instructional approach, it is valuable to examine it through the lens of established and well-researched theories and approaches of teaching and learning. Therefore, we identified which theoretical foundations were used in research on Escape Rooms as learning tools and took a look at the extent to which and where they are represented. For this purpose, a systematic review was conducted, which resulted in the identification of 24 articles containing a total of nine theoretical foundations. It is presented how these approaches are applied in EERs and how they are interrelated. Furthermore, we developed six patterns that illustrate the integration of the found theories into the articles. The integration of these theoretical approaches ranges from general statements on theoretical grounding in EERs without connection to didactic considerations to theoretical grounding with empirical validation. Result of the systematic review is that the theoretical foundation in current research on EERs is weak. Therefore, it is argued that future research should focus more on the interweaving of theory, didactic instructions, and practice to gain a better understanding of mechanisms behind successful learning environments with EERs.