This study explored the mentoring experiences of three underrepresented (UR) women in science, technology, engineering, mathematics, and medicine (STEMM) doctoral programs and how they perceived these mentoring experiences to have shaped their career pathways. Research shows that UR women are graduating from doctoral programs at higher rates than ever, yet are still facing disparate levels in STEMM workplaces (NSF, 2015; Pew Research Center, 2018). In STEMM programs, the mentorship provided can play a significant role in a UR student's experience, especially in regard to psychosocial needs and career-enhancing opportunities (Estrada, Hernandez, Schultz & Herrera, 2018; Felder & Barker, 2010; Griffith, 2010; Lewis, Martina, McDermott, Trief, Goodman, Morse, LaGuardia, Sharp & Ryan, 2016; Lisberg & Woods, 2018). Qualitative methods were used to best understand how each participant made meaning of their mentoring experiences and give voice to an underrepresented population (Merriam, 1998). Data was gathered through in-depth interviews and reflexive journal entries with each participant. Data was analyzed and interpreted using a multi-case study approach through the theoretical lens of social cognitive career theory (Lent, Brown, & Hackett, 1994). The study found three overarching themes: (1) the power of a mentor to support, (2) the power of a mentor to hinder, and (3) the power of alternative support. This research study sheds light on positive and negative mentoring experiences of UR women, as well as other key factors of the student's experiences including their identities, their personal motivations, and communities of support. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]