The “leaky pipeline” metaphor describes the greater likelihood of women and girls to leave STEM fields at every point, relative to men and boys. Gender disparities occur both in recruitment—that is, who chooses to enter a STEM pathway—as well as retention—that is, who chooses to persist in a STEM major or occupation. In addition, women who persist in STEM careers are less likely than men to reach top levels of leadership in those careers. The “leaky pipeline” metaphor describes the greater likelihood of women and girls to leave STEM fields at every point, relative to men and boys. Gender disparities occur both in recruitment—that is, who chooses to enter a STEM pathway—as well as retention—that is, who chooses to persist in a STEM major or occupation. In addition, women who persist in STEM careers are less likely than men to reach top levels of leadership in those careers. Purpose: This paper describes and compares, in quantitative terms, female enrolment on STEM programs within Spain's vocational education and training (VET) system, analyzing the proportion both overall and by occupational group, while also examining the trend in these figures and the extent of progress. Approach: Female enrolment on STEM programs in VET is analyzed at two distinct points: entry and completion. On the one hand, this paper analyzes the proportion of women entering STEM programs based on the number and distribution of women enrolling on STEM vocational education and training courses. On the other, it examines female representation among all holders of STEM qualifications, considering those graduates to represent the potential workforce leaving the education system. Moreover, its studies system efficiency in terms of course completion within the designated time, doing so via the completion rate. Findings: This detailed quantitative breakdown by occupational group reveals a clear gender gap as regards female participation in STEM VET programs. Particularly noteworthy aspects of this difference between the genders are the low number of women attracted to these VET courses, the level of female representation across the STEM occupational groups and their completion rate at the end of the training and learning process. Conclusions: It is important to note that the scarcity of studies of this issue in Spain, especially quantitative ones, shows the limited scientific attention paid to analyzing the gender gap in STEM subjects in the country’s VET system. We therefore believe that this paper's innovative and socially relevant nature makes a valuable contribution to the field, since it represents one of the first steps towards employing scientific research into Spanish VET to help understand and characterize this field that is so important to achieving equality of opportunities for men and women and to advancing sustainable and resilient development in Spain. Finally, it is important to underline that this is an initial analysis of an area that will require further theoretical and empirical development in future years.