This study employed social cognitive theory and social cognitive career theory (SCCT) as foundations to explore the influence of high school students' beliefs about female gender roles and female engineer role models on science, technology, engineering, and mathematics (STEM) self-efficacy and professional commitment to engineering. A total of 88 students from a national girls' high school participated in STEM project-based learning. A survey questionnaire named The STEM Self-efficacy and Professional Commitment to Engineering Questionnaire, developed by the researchers, was administered to collect data, and a structured equation model was employed to confirm the multi-theoretical model developed in this study. The results of this study show that enhancing the gender role beliefs and engineer role models of female students may increase their STEM self-efficacy and professional commitment to engineering. In other words, the female high school students' professional commitment to engineering model can explain students' intentions for future engineering careers. Thus, this study suggests integrating STEM project-based learning into the curricula of various schools and integrating female engineer role models into STEM project-based learning activities for female students, which can enhance female high school students' STEM self-efficacy and professional commitment to engineering.