This study examined negative stereotypes of science, technology, engineering, and mathematics (STEM) professionals as predictors of math/science interests and career goals in a sample of high school students. In a scale development study, results of an exploratory factor analysis (N = 341) indicated a single-factor structure best represented items for the Math and Science Stigma (MASS) Scale—a measure of negative stereotypes of STEM professionals. In a follow-up study, structural equation modeling was used to confirm the factor structure of the MASS. Further analyses showed that a model with STEM stereotypes depicted as a proximal contextual barrier to math/science career interests and goals fit the data well. STEM stereotypes were a significant predictor of math/science self-efficacy, math/science self-efficacy was a significant predictor of math/science interests, and interests predicted math/science career goals. The relationship between STEM stereotypes and math/science interests was explained by self-efficacy. Results are discussed in terms of decreasing negative stereotypes of STEM professionals and enhancing high school students’ interests in STEM careers.