Disciplinary identity, or connection to a particular academic discipline, is constructed through a developmental process across a scholar's academic life course. Using unique data from an online survey of students at four different types of colleges and universities, this study investigates the extent to which disciplinary identity among undergraduate researchers is connected to their human and social capital and differs between social and natural scientists. Disciplinary identity for natural scientists is correlated with mentoring, being a first-generation student, and having a disability, whereas disciplinary identity for social scientists is correlated with only one factor: grit. Implications for institutions and undergraduate programs desiring to enhance the connection between students and their fields of study are discussed.