In this study, a sociocultural perspective was adopted to understand the interplay between identity and agency in a context of science education reform in China. The manifestation of agency and the interaction between identity and agency were examined with two beginning science teachers teaching with practical work in high school. As part of this study, the identity formation of beginning science teachers was conceived as a site for locating and investigating teacher agency. Based on multiple data sources, we identified six spaces in which the two participants’ agency manifested: (1) personal characteristics; (2) personal beliefs; (3) interactions with students; (4) interactions with colleagues; (5) curriculum materials; and (6) high-stakes examinations. In each space, the two participants’ agency contrasted in terms of perspectives and actions: one was passive, less confident and negative, whereas the other active, more confident and positive. Moreover, it was found that their contrary actions were the result of different perspectives. Based on the findings, a model of the interplay between the identity and agency of an individual science teacher is proposed in a context of curriculum reform. The implications of this model for future research and science teacher development are discussed.