The competence to work together and co-create with others outside one's own scientific domain, culture or professional practice is a critical competence for engineers to respond to global challenges. In this context, boundary crossing (BC) competence is crucial. We reflect on a university-wide participatory action research educational innovation project for developing and implementing BC in its education, draw conceptual and practical lessons learned and identify success factors. The BC theory and its four learning mechanisms (identification, coordination, reflection, transformation) are introduced and we argue that they provide a solid foundation for BC competence development in courses and curricula. We show that BC can relatively easy be implemented in existing education, yet it is crucial to use experiential types of learning to make this rather abstract concept tangible for both teachers and students. Two key lessons learned for developing BC education are to see BC competence as a generic competence and boundaries as learning opportunities.