Latinas often experience a double bind as they navigate STEM trajectories, a result of multiple layers of marginalization associated with their intersecting identities. Although developing robust science identities is key to the persistence, success, and sense of belonging of minoritized students in STEM (Carlone & Johnson, 2007; McGee, 2020), many Latinas struggle to identify themselves as science people. Using a testimonio approach, the present study explored how seven Latinas pursuing vertical science transfer pathways at a Hispanic serving community college in Northern California built their science identities, and how mentoring relationships contributed to that process. Testimonio data were collected through individual writing prompts and individual and focus group interviews. Latino Critical Race Theory (Delgado Bernal, 2002; Villalpando, 2004), intersectionality (Crenshaw, 1989), Carlone and Johnson's (2007) model of science identity, and Yosso's (2005) model of community's cultural wealth were used as conceptual frameworks. This study builds on and expands existing research in multiple ways. First, it intentionally centered Latinas' positionalities and cultural wealth as key aspects in their science pathways, mapping how the process of building their science identity was shaped by participants' intersectional identities as Latinas, daughters of immigrants, and first-generation Latina college students. Second, this study amplified the role of the Hispanic serving community college, which became a place where participants could explore their place in science, engage in counterspaces (i.e., spaces, physical or ideological, that facilitate collective processing and resistance of experiences of marginalization, usually connected through shared elements of identity) (Shirazi, 2019), and interrogate Eurocentric meanings of science and being a science person. Finally, this study expanded the scope of mentorship beyond faculty-student dyads, including family and community members, and student support professionals at the community college. Participants' testimonios showed how their science identities were impacted by the opportunities mentors provided for them to develop their science competence and perform science skills, mentors' validation of participants' abilities and potential in science, and mentors' support in leveraging and expanding their community's cultural wealth. These findings suggest the need for community colleges and STEM departments to create intentional counterspaces for Latinas; expand professional development for faculty, student support professionals, and administrators on culturally competent practices; create opportunities for Latinas to explore community-based approaches to science; and design STEM mentoring programs guided by critical and culturally relevant frameworks. Future research should explore how specific groups of Latinas (e.g., Chicanas, Afro-Latinas) position themselves in science and build their science identities; explore the experiences of mentors at Hispanic serving community colleges; examine the experiences of Latinas who have not identified mentors or have sustained non-effective mentoring relationships in their science trajectories; and move towards more integrated models that examine the impact of effective mentorship on core aspects of Latinas' identities beyond their science identities. [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.]