The field of engineering continues to be highly male dominated, with women receiving only 20% of undergraduate degrees in the US and comprising only 15% of the workforce. Barriers to entry are experienced by girls as early as age five, when children become cognizant of the stereotype that girls are worse than boys at math. This dissertation sought to understand the barriers to entry and success faced by women in engineering, as well as the types of inclusive instructional pedagogy, from elementary school to college, that could help remove those barriers. We identified the most common barriers through survey data collected from 176 undergraduate engineering students at a university in Southern California. We subsequently analyzed the impact of a novel partnership program developed between a freshman mechanical engineering course and after school elementary program on the participating undergraduates and elementary students. We relied on pre-post student interviews, video-recorded program sessions, and documentation of student work to investigate the elementary students’ engineering identities and the undergraduates’ self-efficacy beliefs, as they developed over the course of the 10-week program. Three themes emerged from our analysis. First, barriers to entry and success in engineering for women began early and were unrelenting (Chapter 2). Women were introduced to engineering later in their lives and once enrolled in undergraduate programs, women were significantly more likely to have low beliefs in their engineering abilities and expectancies for future success, even after controlling for ability. Second, well designed undergraduate engineering curricula can substantially help boost engineering students’ self-efficacy beliefs (Chapter 3). Scaffolded project-based learning helped novice students develop the mastery experiences necessary to feel confident in their abilities and client-led design gave students the opportunity to identify as engineers. Elementary children proved to be ideal clients for freshman engineering students because they simulated the engineer-client relationship in a low-stress environment. Third, highly collaborative engineering programs which leverage peer groups, role models, and inter-group collaboration can help elementary students develop identities as engineers; this was especially impactful for girls (Chapter 4). Working with peers on a collaborative project encouraged students who were initially uninterested in engineering to engage in the activities and engineer role models helped students better identify as engineers. Our work supports and extends the literature by identifying common barriers for girls and women in the field of engineering and analyzing the link between well-designed engineering education and both elementary and undergraduate students’ ability beliefs. Our results suggest that to narrow the gender gap in engineering young girls need more regular exposure to engineering in highly collaborative environments and undergraduate engineering programs should be designed to support women’s development of engineering competence beliefs through mastery experiences with clear connections to engineering as a career.