Higher education institutions are being called to provide leaders capable of operating in increasingly complex environments (Astin & Astin, 2000; Daloz Parks, 2005; Longo & Gibson, 2011; Rost & Barker, 2000). As immersion into these complex environments has been found to assist students in developing leadership capacities, mentoring is needed to help support students during these immersion experiences. Researchers have explored how mentoring influences leadership development (Campbell, Smith, Dugan & Komives, "in press"; Collins-Shapiro, 2006; Gleason, 2009; Jabaji, Slife, Komives, & Dugan, 2008), but it is valuable to study mentoring effects within different institution types based on Carnegie Classification, as different environments have different influences on student effects and outcomes. There currently exists a lack of literature in this area. This post-positivist, quantitative study utilized a secondary data set, the 2009 Multi-Institutional Study of Leadership (National Center for Leadership Programs, 2011) to understand how mentoring and leadership development compare among institutions of different Carnegie Classifications. Respondents in this data set attended 101 institutions in the United States that had responded to an open call in the summer of 2008. A subsample of 57,713 of the original 115,632 cases contained responses related to mentoring for this study. The Multi-Institutional Study of Leadership utilized the Socially Responsible Leadership Scale as its primary scale, which was developed by Tyree (1998) and measures the core values of the Social Change Model. Seven research questions provided the foundation of the study, which was operationalized in Astin's (1993) Input-Environment-Output (I-E-O) Model. Variables in the study were analyzed utilizing descriptive statistics; inferential statistics, such as analysis of variance (ANOVA); and multiple sequential hierarchical regression analyses. The findings of this study provide insightful information for researchers, practitioners, and policy makers. Understanding how mentoring influences leadership development in different institution types can help improve practice and provide insight for additional research. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]