Research suggests that elementary school is a crucial period for sparking students' long-term interest in science and consideration of a STEM career. Teachers influence students' dispositions towards science; therefore, it is important to consider elementary teachers' identity development, a preservice teacher's own voice and self-image, with science as a factor in science education. This longitudinal, qualitative study examines the experiences that served as barriers or supports to elementary Master of Teaching preservice teachers' science teacher identity development. Six preservice teachers were interviewed at the beginning of their graduate teacher education programs and again during their first year of teaching. Our findings indicate that identity development of future elementary teachers begins during their own elementary school experiences as a student and spans through their teaching practicums. Barriers to science identity development included prior elementary science experiences/lack of interest, science content and coursework requirements, practicum experiences, and socioeconomic status. Supports that bolster elementary teacher identity for instructing science included hands-on/inquiry-based science coursework, prior experience in schools and working with children, positive practicum experiences, and support from family and friends. This research indicates that in order to develop more rigorous elementary science teacher preparation programs, in regard to instruction and self-efficacy, educators and public policymakers will need to provide a series of supports for future science teachers ranging from their initial elementary school experiences through their practicum placements.