National identity is one of the most important forms of ideology that affects human behaviours. Yet, the issue of whether it influences history teachers' subject matter knowledge or teaching practice is overlooked most of the time. With regime change in Taiwan, history curriculum and textbooks are no longer dominated by a China-centred narrative; more Taiwanese history is included in the curriculum. Given the fact that the Taiwanese are split on the issue of national identity, it is important to understand if and how teachers vary in their historical knowledge and instruction. This study examines the issue by investigating the relationships between Taiwanese junior high school history teachers' national identities, their subject matter knowledge and teaching practices. The result indicates that teachers' national identities significantly relate to their historical knowledge and conceptions about history, but bear no relationship to their teaching approaches. Pro-independence teachers have significantly more knowledge in both Taiwanese and Chinese histories and have better conceptions about the nature of history, but they do not necessarily choose to provide students multiple perspectives and interpretations. The implications for democratic citizenship education and teacher education are discussed. (Contains 2 notes and 6 tables.)