The purpose of this qualitative study was to investigate preservice elementary teachers' science teacher identity development during their participation in the field-based science methods course and a year after. Grounded within the Feiman-Nemser's thematic framework of learning to teach, this study utilized a case study approach aimed to examine the experiences that contributed to formation of science teacher identities of two participants uniquely positioned in the teacher education programs at the two sites, USA and Canada. Data collected over a year included science autobiographies, reflective journals, interviews, classroom observations, and artifacts. The analysis of the data revealed that experiences and interactions within prior science courses, science methods course and classroom teaching, and the program itself (a year after), accounted for the changes in how and in what the ways the two preservice teachers "think," "feel," "know," and "act" as a teacher of science. Findings indicate the importance of the framework of learning to teach in shaping preservice science teachers' identities. The study includes implications for preservice teacher education programs and research.