There is a lack of literature that has investigated the relationships between stereotype threat, impostor phenomenon, and other related constructs on career development, particularly for women in STEM. While various resources (National Science Foundation, 2013; Sax, Kanny, Jacobs, Whang, Weintraub, & Hroch, 2016; US Department of Labor, 2014) have highlighted the gender gap and "leaky pipeline" in STEM, it is important to further investigate and understand why these phenomena occur and continue to persist. In this study, I used a mixed methods approach which used a quantitative SEM analyses and qualitative interview to further examine the paths between chilly climate, impostor phenomenon, stereotype threat, science self-efficacy, fear of failure, fear of success, academic major satisfaction, and persistence in STEM in a sample of undergraduate females. Several hypotheses were formed in order to better understand the mediation effects of these variables upon one another. Stereotype threat was found to be endorsed at a lesser rate than anticipated, while impostor phenomenon was endorsed at a higher rate. Science self-efficacy was also found to play an important role in the predicted relationships among variables, relating to both academic major satisfaction and persistence. These quantitative results were supported by data gathered in qualitative interviews. Implications for research and practice around concerns of impostor phenomenon, stereotype threat, and fears of failure and success are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]