Graduate students from historically underrepresented minority (URM) groups (those who identify as Black/African-American, Hispanic/Latino/a/x, Native American, Native Hawaiians/Pacific Islanders and/or Alaska Natives) encounter systemic and institutional hindrances to degree completion when enrolled in STEM doctoral programs at predominantly white institutions (Guiffrida & Douthit, 2010). Support networks have been identified as an important component for retention and success for graduate students from URM groups (Carlone & Johnson, 2007; Clewell, 1987; Johnson-Bailey, Valentine, Cervero, & Bowles, 2008; Joseph, 2012; Sweitzer, 2009). This study investigates the composition and structure of URM graduate students’ support networks, where their support comes from, in what capacity, if URM women graduate students gravitate toward support systems that match their cultural/racial background or gender identity, and if URM students who complete degrees experience feelings of loneliness and isolation, which is a contributing factor to underrepresentation of students from these minority groups (Gloria, Robinson, Hamilton, & Willson, 1999). Data for this study were collected through a longitudinal interview process combined with four social network surveys per individual as students progressed through their programs. Interview data allowed for longitudinal tracking of social support network members, which was triangulated with the data from the social networking surveys and analyzed through the lenses of egocentric network analysis, constructivist grounded theory, and critical race theory. Many participants in this study needed and found a strong support network through student organizations that matched their cultural/ethnic/racial background. Countless students struggled with feelings of isolation and loneliness, yet finding support from campus groups helped fill this void. The final data collected after most of them had left graduate school showed significant discrepancy between their reported robust social network and their open-response data where they indicated a significantly reduced social network and the onset of feelings of loneliness. This dissertation, while focusing on social support networks for these URM graduate students at predominantly white institutions, has the potential to address social justice issues and equal opportunities for those identifying as Black/African American and Hispanic/Latino/a/x, encourage the importance of reaching a critical mass in higher education settings, work toward combating systemic racism, add greater diversity and perspectives to the more elite careers that these degrees will lead to, and show the importance of having a social support network while pursuing a prestigious degree, the PhD.