Based on the theoretical taxonomy of supports and barriers and Social Cognitive Career theory, this chapter contributes to the existing literature on STEM women’s pathways by qualitatively examining environmental supports and barriers that girls and women experience in all developmental stages, from childhood to professional life. The overarching purpose of this chapter is to synthesize and summarize the multidimensional barriers that affect, impede, or prevent girls and women from choosing STEM educational/career trajectories and the supports that facilitate their advancement and retention in STEM career trajectories across three developmental stages: childhood, adolescence (high school and university study), and adulthood (professional life). A core finding from this study is that women are strongly dependent on external social agents, such as parents, teachers, peers, employers, and spouses, in all developmental stages, who can play a dual role, either supporting the girls’ and young women’s interest in STEM and providing mentorship or discouraging them from being engaged with STEM.