Continual underrepresentation of racial/ethnic and female students in STEM has called for the examination of the barriers encountered by these groups on their path into this field and to examine the factors that help students’ degree attainment. However, research regarding STEM education has primarily focused on the undergraduate level which limits scholarly evaluations of why students persist in the field for the long-term such as into professional degrees. Therefore, this qualitative research reports on how underrepresented minorities who are pursuing graduate degrees gained entrance into STEM and the strategies they used to persist, not only during their undergraduate studies, but beyond into their graduate work. In this study, 18 in-depth interviews were conducted with marginalized students pursuing a graduate STEM degree at a university in California. Results from this study suggest the significance of individual-, interpersonal-, and institutional-level factors in both the students’ entrance and persistence in STEM. In this study, interpersonal- and institutional-level factors were demonstrated through the support and guidance received by personal networks and/or on-campus resources. These supports most notably came in the form of emotional, academic, and financial assistance. However, the contributions of interpersonal- and institutional-level support were especially noteworthy in the students’ entrance into the field. In comparison, the impact of individual-level factors such as STEM passion, self-efficacy, and personal effort were most notable in the students’ development of four persistence strategies. These four strategies were: remembrance of STEM passion, grounding through positive STEM experiences, relying on social support, and establishing community in the STEM space.