This study investigated the formation of non-native English speaker teachers' beliefs about language choices in South Korean elementary school English classrooms. While most research has looked at how the classroom context affects language choices, this study delved into teachers’ past learning experiences in order to establish how teachers’ beliefs about target and first language uses in the classroom were formed. Focusing on different stages of belief development by dividing beliefs into an initial assumptions stage, a tentative attitudes stage and a firm beliefs stage, it discovered how primary and secondary influences acted upon the evolution of teacher beliefs about language use in the classroom. Although set within an EFL context, the process of identifying the different stages of belief development and the sets of influences acting on this development at different stages of a teacher’s career can be applied to a variety of contexts and beliefs. The paper includes an explanation of the methodology used to gather the data, as well as explores possible implications for language teacher education programs which seek to include a more interpretative epistemological stance on language teacher education in order to better meet the needs of new and experienced teachers.