This study examined the processes that contributed to students’ aspirations for STEM careers and unpacked the relationships between students’ self-concept in science and mathematics learning, perceived parental expectations, perceptions of STEM professionals, career outcome expectations and STEM career aspirations. Structural equation modelling was used to analyse quantitative survey data of 2,477 primary and secondary school students studying in seven Asian regions (Hong Kong, Malaysia, Mainland China, Indonesia, Korea, Taiwan, and Singapore). The results demonstrated that students’ self-concept, perceptions of STEM professionals, and their career outcome expectations all significantly and positively predicted their aspirations for STEM careers. However, this study failed to establish a direct relationship or positive correlation between perceived parental expectations and STEM career aspirations. Students’ self-concept negatively predicted their career outcome expectations related to seeking parental approval. While no significant positive effects of perceived parental expectations on career aspirations were found, an indirect effect of perceived parental expectations on STEM career aspirations via career outcome expectations was observed. Moreover, career outcome expectations mediated the relationships between students’ STEM career aspirations and their perceptions of STEM professionals more strongly than self-concept. The implications of these results for STEM education are discussed.