This study examines pre-service primary school teachers' (PSTs') possible selves in relation to science teaching and the ways in which these possible selves change over time. This longitudinal study adds to the body of knowledge by examining PSTs' possible selves at various time points throughout their teacher preparation: three PSTs, selected from a wider sample, were interviewed three times about their future aspirations as science teachers. Narrative analysis was applied to show the changes in three PSTs' possible selves in response to the science methods course and teaching practicum. PSTs articulated general, collective and specific hoped-for and feared possible selves. Our findings highlight the changes in the possible selves that pertain to their cognitive and affective dimensions and occurred in different stages of teacher education. These changes were significant for the development of PSTs' identity. The implications of these findings are discussed in the context of science teaching.