STEM (Science, Technology, Engineering and Mathematics) enrolments in higher education are declining while the STEM gender gap of female underrepresentation seems to widen. The present study addresses both issues by exploring how the fit between a student's vocational interests and the STEM field contributes to a (non-) STEM study choice. Data was collected in the unique setting of an open access and low cost higher education system, which allowed for study of vocational interests without unwanted influence of admission conditions. Specifically, we assessed the interest fit of N = 9162 first-year Belgian university students with (1) the STEM field (i.e., STEM fit) and (2) their specific program of choice (i.e., program fit). Results indicated STEM fit indeed predicted STEM study choice, with a stronger effect in female students. Results also indicated that female students showed a better specific program fit. In order to promote student STEM enrolment and address the gender gap, the present study therefore advocates a gender-specific approach to attract more students with appropriate interest profiles.