Background: Engineering requires new solutions to improve undergraduate performance outcomes, including course grades and continued enrollment in engineering pathways. Belonging and engineering role identity have long been associated with successful outcomes in engineering, including academic success, retention, and well-being. Purpose: We measure the relationships between belonging and role identity at the beginning of a first-year engineering course with course grade and continued enrollment in engineering courses. We test the effect of an ecological belonging intervention on student belonging, course grade, and persistence. Method: Students (n = 834) reported their sense of belonging in engineering, cross-racial experiences, engineering performance/competence, interest in engineering, and engineering recognition before and after an in-class intervention to improve classroom belonging ecology. Through a series of longitudinal multigroup path analyses, a form of structural equation modeling, we tested the predictive relationships of the measured constructs with engineering identity and investigated differences in these relationships by student gender and race/ethnicity. Findings: The proposed model predicts course grades and continued enrollment, providing insight into the potential for interventions to support first-year engineering students. Group analysis results demonstrate the difference in the function of these psychosocial measures for women and Black, Latino/a/x, and Indigenous (BLI) students, providing insights into the potential importance of sociocultural interventions within engineering classrooms to improve the engineering climate, engagement, and retention of students. Implications: The results highlight the need for more specific, nuanced theoretical investigations of how marginalized students experience the engineering environment and develop social belonging and engineering role identity.