This paper aims to present some conceptual insights into the research paradigm of complexity that deals with such problems like sustainability, education, and, more specifically – sustainability education. The transdisciplinary perspective and cognitive approaches of a hermeneutical cycle and semantic waves used in argumentation assist in grasping the essence of complexity and the main principles of complex dynamic systems. The comparison of simple, complicated and complex systems in a field of sustainability education provides an example of using complexity thinking with social systems. Then the complexity in an epistemological context, as the research paradigm, could be used for dealing with the challenging problems of sustainability, education and sustainability education from the point of view of post-normal science. The concept of transdisciplinarity has been developed as a research framework starting from the general approaches to its application for sustainability, education and sustainability education. The specific types of collaboration in educational research for sustainability and the modes of knowledge produced by transdisciplinary research in this field will be described, ending with reflections and suggestions for further analysis.