Local knowledge is increasingly considered to be beneficial for the development of new, more adequate and sustainable solutions to a wide range of social and environmental problems. The term ''transdisciplinary research'' is used to label a range of research practices in which knowledge from different social and academic actors is integrated. It can be seen as a new form of learning and problem solving, which helps to meet the complex challenges of society, such as sustainable development. In order to understand complex processes of problem solving we need to take a closer look at the way in which these take place, especially with respect to the (co)creation of knowledge. By defining and (re)shaping theoretical concepts about knowledge, knowledge creation, and knowledge integration, this chapter aims to contribute to the epistemological basis of transdisciplinary research.