The purpose of this qualitative study was to investigate the contributions of pre-service teachers' memories of science and science education, combined with their experiences in a STEM-focused teacher preparation programme, to their developing identities as elementary school teachers of science. Data collected over three years include a series of interviews and observations of science teaching during elementary teacher preparation and the first year of teaching. Grounded within a theoretical framework of identity and using a case-study research design, we examined experiences that contributed to the participants' identity development, focusing on key themes from teacher interviews: "memories of science and science instruction," "STEM-focused teacher preparation programme," "field experiences," "first year of teaching," and "views of effective science instruction." Findings indicate the importance of exposure to reform strategies during teacher preparation and are summarised in main assertions and discussed along with implications for teacher preparation and research.