<p>Urban transformations towards sustainability require cooperation among various stakeholders. There is an increasing amount of research on how to facilitate these cooperations, particularly regarding necessary governance modes and capacities. However, studies that specifically examine the cooperation among three key actor groups, or in short, the trialogical cooperation, are limited. This study focuses on the trialogical cooperation between city makers, city administrators, and transformative researchers, as these groups play a crucial role in implementing sustainability measures. Although many challenges related to multi-actor cooperation have been discussed in literature, they have not widely been systematically explored. Existing studies often concentrate on specific projects without adequately analyzing the perspectives of individual stakeholders. This article offers a broader view by providing insights into the perceptions of participants involved in this trialogical cooperation in projects throughout Germany. These perceptions were gathered through reflexive workshops and group discussions. As a result, a conceptual model to analyze key relations and factors influencing trialogical cooperation for urban sustainability was developed. This model is presented in this article and can be utilized to systematically examine various forms of multi-actor cooperation. We identify three key relations that significantly shape the studied trialogical cooperation: 1) the interaction between existing contexts and current forms of cooperation; 2) the mutual influence between individuals and institutions; and 3) the enhancement of collective and individual transformative capacities through reflexive learning. Through this study, we contribute to a deeper understanding of multi-level challenges within one of many (trialogical) cooperations for urban transformation towards sustainability.</p>