After the introduction of Learner Centred Education in Namibia, a number of studies were conducted on how teachers either perceived learner centred education or implemented it. However, very few studies investigated the teachers' understanding of both subject matter knowledge and pedagogical content knowledge; primarily, how they understand and develop key concepts. The purpose of this study was to investigate how Grade 5 teachers' understand and develop key concepts in Social Studies in selected schools in Namibia. The study focused on three teachers in three primary schools in the Caprivi educational region of Namibia. These teachers were purposefully selected as graduates of the teacher education programme instituted at the time of the Namibian education reform process. As a teacher educator, my main motive of conducting this study was to gain a better understanding of some of the issues that have been raised about these graduates' lack of content knowledge. The study adopts a qualitative approach and seeks to investigate (a) how the three teachers in this study understand key concepts and (b) the strategies they use to develop such concepts. Three data collection instruments were employed: interviews, document analysis and class observations. The findings indicate that despite the training that all three teachers in this study received, their understanding of the concepts they taught is problematic. Furthermore, some of the strategies that the teachers used did not bring about learning with understanding. The results of the study revealed how these teachers' problems with concepts and the development of conceptual understanding are related to specific issues and can be attributed to a number of factors. Because of this, the study has provided valuable insights into aspects of teacher education that need to be addressed both in terms of in-service and pre-service programmes to support teachers in teaching for understanding, a key idea underpinning the reform process.