Why are some youth more likely to think of themselves as a science kind of person than others? In this paper, we use a cognitive social-theoretical framework to assess disparities in science identity among middle school–age youth in the United States. We investigate how discovery orientation is associated with science interest, perceived ability, importance, and reflected appraisal, and how they are related to whether youth see themselves, and perceive that others see them, as a science kind of person. We surveyed 441 students in an ethnically diverse, low-income middle school. Gender and race/ethnicity are associated with science identity but not with discovery orientation. Structural equation model results show that the positive association between discovery orientation and science identity is mediated by science interest, importance, and reflected appraisal. These findings advance understanding of how science attitudes and recognition may contribute to the underrepresentation of girls and/or minorities in science.