Background/Context: The underrepresentation of students from lower socioeconomic status (LSES) backgrounds among college graduates with science, technology, engineering, and mathematics (STEM) degrees, and consequently in STEM occupations, is a concern with respect to reducing, perpetuating, or increasing social inequality. The loss of their talent and creativity also poses a threat to the future of the U.S. economy, scientific knowledge generation, and national security. This study uses two theoretical frameworks—bounded rationality and effectively maintained inequality (EMI)—to identify the pathways toward STEM for students from lower and higher SES backgrounds, given the well-documented differences in their family resources and opportunities to learn, amount of cultural capital, and risk aversions. Purpose: The study identifies factors related to LSES students’ odds of declaring and graduating with a STEM degree and tests whether those factors work in similar ways for students from higher socioeconomic groups. The study contributes to understanding the roots of the underrepresentation of LSES students in STEM majors and occupations. Research Design: We use a mixed-method sequential explanatory design that draws from two complementary sources of data, one quantitative and one qualitative. Using multilevel logit models, the quantitative data set explores how SES influences students’ choices regarding whether to pursue a STEM degree. The qualitative data set further explores the relationships found in the quantitative data specifically for the case of LSES students through analysis of in-depth interviews. Findings: Quantitative analysis finds that LSES students’ socioeconomic background is related to their reduced opportunities to learn and reduced information resources, lessening their adequate academic preparation for success in STEM majors. Qualitative data indicate that risk avoidance—specifically, perceptions of risk and ideas of future income stability—play an important role in LSES students’ decisions to major in STEM. In addition, LSES students possess insufficient data to make informed decisions while in high school regarding course selection that would better enable their pathways into STEM, and to navigate into college success. Conclusions: To foster equity in access to postsecondary educational resources, it is crucial to offer all students access to high-quality academic opportunities before enrolling in college. Furthermore, high schools must ensure that students have access to explicit information about college and what various majors entail. We advocate that all students should have information on all options available so they can make well-informed decisions that match their abilities and preferences. Students’ access to and preferences for certain majors should not be conditioned on their socioeconomic background.