The recruitment of undergraduate students in England into teacher education is a recognised challenge with recruitment targets having been missed in nine of the last 10 years. The recruitment shortfalls are most acute within STEM (Science, Technology, Engineering, and Mathematics) subjects. This qualitative study explores which aspects of teaching attract and deter undergraduate STEM students from entering the profession, and which aspects of the vocation are unknown to undergraduates. Participants consisted of 267 STEM undergraduate students (73% White British; 57% female) from a broad range of UK universities. The sample reflected the sociodemographic characteristics (e.g., ethnicity, gender, socioeconomic background [SEB]) of undergraduate students in British universities. Data for this study consisted of responses to open-ended questions about interest in teaching generated after exposure to an experimental vignette intervention consisting of 12 teaching-related vignettes, each exhibiting a different motivation for entering teaching. Data were coded using reflexive thematic analysis and multiple indexing. Findings from this study suggested that participants were primarily attracted to teaching by the perceived emotional rewards of supporting young people, and the tangible benefits (e.g., holidays) made the career desirable. However, participants also felt an imbalance between the pull and push factors of teaching. Workload and negative treatment of teachers were seen as the central deterrents to entering teaching; however, we also found that there was a significant knowledge deficit about what teaching entails.