Research shows that mentoring relationships between STEM students and faculty contribute to the development of a strong science identity, which in turn aids in racial/ethnic minority students’ pursuance of STEM degrees, matriculation into graduate STEM programs, and entrance into STEM careers. However, research on the effects of mentorship and identity in STEM exhibits two weaknesses: mentorship relationships tend to be conceptualized as static, versus dynamic, and as a result, mentorship relationships tend to be operationalized as dichotomous (e.g., as something students do or do not have). In this chapter, we conceptualize the mentorship relationship as dynamic and operationalize it through sequence analysis of The Science Study—a longitudinal dataset that captures the experiences and outcomes of marginalized racial/ethnic minority students in STEM. We find that one-fourth of students in the sample experienced mentorship loss and that consistently maintaining a mentorship relationship is associated with greater persistence intentions than never having a mentorship relationship or having a mentorship relationship that prematurely ends. Our results underscore the importance of longitudinally tracking mentorship relationships—ideally with an eye toward identity-relevant resources gained therein—which may further strengthen mentorship initiatives for racial/ethnic minority student retention in STEM programs.