This chapter explores the notion of historical awareness in relation to using primary historical sources in the teaching and learning of mathematics. It does so through the analysis of two teaching experiments originally designed from different, yet related perspectives. We present an analytic framework for identifying historical awareness and use it to analyze two cases in order to explore and discuss how and in what sense using primary historical sources in the mathematics classroom have potential to develop students’ historical awareness. Finally, we point toward more general challenges in mathematics education that historical awareness may be suited to address and articulate.