Women and underrepresented minority (URM) undergraduates declare and complete science, technology, engineering, and mathematics majors at different rates in comparison to majority groups. Explanations of these differences have long been deficit oriented, focusing on aptitude or similar characteristics, but more recent work focuses on institutional contexts, such as academic climate and feelings of belonging (fit). This study examines the experiences of women and URM students in engineering undergraduate programs, focusing on how they fit, experiential factors affecting fit, and how fit is mitigated by social relationships from their networks and organizations in which they participate (i.e., social capital). Thematic analysis of 55 women and URM interviewee responses shows that students who fit well were those with majority characteristics, including race (i.e., White, White-passing) and gender (i.e., men, masculine appearance), and those in groups well represented in their programs numerically (i.e., men, Asian). In contrast, women and Black students encountered threats to their fit due to stereotyping from bias and differential treatment from others (i.e., being excluded from group work). However, students received advice from their social networks (i.e., family, professors) in which they were warned to expect discrimination, or through organizations in which they participated (i.e., National Association of Black Engineers) where their sense of community was expanded. The advice and resources provided through this network-based and participatory social capital mitigated fit for women and Black students, albeit in different ways, helping to preserve their feelings of belonging and promote their persistence in engineering. We offer suggestions to enact university policies to increase access to social capital with homophilious alters and educational opportunities for majority groups.