Privileging elite academic pedigrees in graduate admissions preserves racial and socioeconomic inequities that many institutions say they wish to reduce. To understand this preference, I integrate across perspectives on trust in rational choice, social capital, and social network theories, and use the resulting framework to interpret 68 interviews with faculty reflecting on graduate admissions. Individual and institutional trust networks enable faculty to invest in students' uncertain futures, with trust especially important for interpretations of transcripts and letters of recommendation. I discuss trust networks' consequences for admissions, how they can be expanded, and their relevance for future higher education research.