In the undergraduate and working environments, some science, technology, engineering, and math (STEM) areas remain dominated by males. The purpose of this study was to understand the gendered experience of individuals in STEM majors by assessing students’ math self-efficacy, impostorism (a feeling of intellectual phoniness), and future goals. Based on prior research, an overall conceptual model was proposed and analyzed. Several related precursors including gender role orientation, perceived parental influence, math identity, and theories of intelligence were included in the model. Three hundred six undergraduates (64.38% female) in the colleges of natural science, geosciences, and engineering responded to an online survey addressing these constructs. Based on prior research, hypotheses were created proposing that females would report higher impostorism, lower math self-efficacy, and more femininity than males. I expected that masculinity, perceived parental influence, an entity theory of intelligence, and high math identity would predict the impostor phenomenon. Moreover, I hypothesized that the relation of each of these predictors to impostorism would be moderated by sex. For the next two hypotheses, I proposed that the four sources of math self-efficacy would predict math self-efficacy, but this relation would be moderated by impostorism. Finally, I expected that impostorism would lead to reduced future expectations and aspirations, but that this association would be mediated by math self-efficacy. Results indicated partial support of the study hypotheses, and a revised model was created. Both sexes reported similar levels of impostorism, but females had lower math self-efficacy and greater femininity than males. Masculinity negatively predicted the impostor phenomenon, while math identity and an entity theory of intelligence positively related to the dependent variable. Sex moderated the effect of perceived parental influence such that males’ impostorism was more affected by parental influence than females’. Emotional arousal was a strong contributor to math self-efficacy, but this relation was attenuated by impostorism. Coping with emotional arousal was positively associated with math self-efficacy; however, this association was significantly stronger for low impostors than high ones. Finally, impostors were less likely to expect to go to graduate school or work in a STEM-related field. Implications for schools and professors are discussed. / text