Despite the critical role of peers in the socialization of doctoral students, relatively few researchers have studied types of peer relationships and information exchanged between doctoral students. This study aims to explore doctoral students’ perceptions of their peer relationships and informal peer mentoring within a library and information science program. The authors applied Kram and Isabella’s peer relationship framework developed in organizational settings to examine peer relationship types of library and information science doctoral students. Interviews with 12 doctoral students reveal the existence of cohort, social/academic peer, and other peer groups, which can be mapped onto Kram and Isabella’s continuum of peer relationships, categorized as special, collegial, and information peers; however, this framework suffers from a limitation in explaining dysfunctional peer relationships identified in the study. In regard to differences between peer relationships and peer mentoring, respondents tend to perceive mentoring as a developmental function that takes place in peer relationships. Moreover, the authors propose five types of information exchanged between doctoral students, which are (a) basic, (b) administrative, (c) professional, (d) social, and (e) personal information, and they suggest that peer relationships influence the topical diversity and degree of disclosure in information exchange.