<p>The United States faces a shortage of workers in high demand science, technology, engineering, and mathematics (STEM) fields. To address this shortage, more research is warranted to understand the factors that can support undergraduate students’ persistence and self-efficacy in STEM. Social Cognitive Career Theory (SCCT) explains that students’ self-efficacy in their careers must be examined through a lens of socio-contextual factors, but there is a paucity of research examining the mechanisms which can facilitate the connection between students’ social support and their career self-efficacy. The current study examined how science identity and growth mindset can be mechanisms which facilitate students’ support from faculty into career self-efficacy. Undergraduate students majoring in STEM completed self-report surveys measuring their faculty social support, growth mindset, science identity, and career self-efficacy. Higher social support from faculty predicted higher career self-efficacy through a serial mediation of higher science identity and higher growth mindset. The current study therefore extends the literature by highlighting these mechanisms and discussing implications for these findings for future interventions seeking to support STEM students’ career self-efficacy.</p>