Research suggests that trajectories toward careers in science, technology, engineering, and mathematics (STEM) emerge early and are influenced by multiple factors. This paper presents a longitudinal study, which uses data from 76 high school students to explore how a student’s vocational self-efficacy and interest are related to his or her middle school behavioral and affective engagement. Measures of vocational self-efficacy and interest are drawn from STEM-related scales in CAPAExplore, while measures of middle school performance and engagement in mathematics are drawn from several previously validated automated indicators extracted from logs of student interaction with ASSISTments, an online learning platform. Results indicate that vocational self-efficacy correlates negatively with confusion, but positively with engaged concentration and carelessness. Interest, which also correlates negatively with confusion, correlates positively with correctness and carelessness. Other disengaged behaviors, such as gaming the system, were not correlated with vocational self-efficacy or interest, despite previous studies indicating that they are associated with future college attendance. We discuss implications for these findings, which have the potential to assist educators or counselors in developing strategies to sustain students’ interest in STEM-related careers.