<p>Despite institutional efforts to address gender inequalities, labour market segregation remains a key contributor to the gender pay gap. In this study, we present one of the first experimental evaluations in Spain of a low-cost, one-off intervention featuring a female role model aimed at enhancing adolescent perceptions of STEM subjects and associated career prospects. Our randomised controlled trial shows that exposure to a female mathematician significantly improves adolescents’ perceptions of the usefulness of mathematics, their maths-related career aspirations, and their perceptions of maths-related jobs. For girls, the intervention produces particularly strong effects in the notion that mathematics can help address global challenges such as inequality or global warming. The intervention also increases self-projection in maths-related careers, which is especially relevant given women’s traditionally lower propensity to envision themselves in these roles. Complementary analysis using a large-scale survey of adults in Spain further reveals that maths anxiety, potentially malleable during adolescence, strongly predicts later selection into STEM-related fields. These findings underscore the potential of scalable interventions to promote gender balance in education and to reduce occupational segregation in the labour market.</p>