One of the main challenges in sustainability discourse is its multifaceted nature often requiring that many different disciplines must cooperate in order to achieve progress. This issue also concerns sustainability education. In the article, we highlighted the experiences from the international cooperation of university teachers and researchers with highly diverse professional backgrounds who worked together on developing educational materials for university students in sustainability-oriented courses. The study is based on qualitative, participatory evaluation research, applying two rounds of open-ended questionnaires distributed to the same respondents (n = 18). For the analysis, we used the open-coding procedure for identifying the main categories. The results show some of the opportunities and barriers that emerged in the process of this cooperation. In particular, we discuss the issues related to the high heterogeneity of the group, such as the clashes of the different perspectives on the topics covered, group dynamics issues, trust, facilitation challenges, and also opportunities that such heterogeneity offers. We highlight the importance of open reflectivity in sustainability-oriented educational projects as the key to their successful implementation. Finally, we believe that results of this participatory study are useful in designing new projects aiming at further improvement of academic education in sustainability and sustainable development.