This paper presents the results of a longitudinal study into the mathematical identity of science and engineering students (MISE) in Dublin City University. The goal of the research was to expand on previous mathematical identity research in Ireland by including science and engineering students since they study a significant amount of mathematics at university level. Mathematical identity is considered to be one’s relationship with mathematics, including knowledge of the subject and perception of oneself and others (Eaton & OReilly, 2009, p. 228). This qualitative study was conducted over four years using a narrative approach to mathematical identity (Radovic, Black, Williams & Salas, 2018, p. 29). The study involved 32 participants from science and engineering courses in DCU, including several students of science education who have since qualified as teachers. All participants completed an online open-ended questionnaire on mathematical identity in their first year of university. A further five participants contributed to focus groups and six participants took part in narrative interviews at the final stage of data collection. The conclusions are derived from participants’ mathematical identity narratives which were developed through several stages of data collection involving both thematic and narrative analysis. The findings highlight several issues that affected multiple participants and may affect a broader cohort of students than were included in the study. We also present some unique features of mathematical identity that arose in this context as students transitioned to higher-level education.