Black women undergraduate STEM students at Predominately White Institutions (PWIs) contend with difficult experiences in their academic majors (Charleston et al., 2014; Fletcher et al., 2017; Johnson, 2007; McGee & Bentley, 2017). Black women undergraduate STEM students are battling isolation, microaggressions, chilly climate, and other systemic barriers in their respective disciplines (Charleston et al., 2014; Fletcher et al., 2017; McGee & Bentley, 2017). However, additional research is needed to understand their STEM co-curricular experiences. The study explored the experiences of Black women STEM undergraduate students participating in STEM co-curricular and support programs on a PWI campus. Using a single embedded case design, I used the following research questions to guide the study: How are Black women undergraduate STEM students engaging in STEM co-curricular and support programs at a Predominately White Institution (PWI) in the Southeast? Additionally, using the following sub-questions: What are the experiences of Black women undergraduate STEM students in peer-based STEM support/co-curricular programs? What are the experiences of Black women undergraduate STEM students in research-based STEM support/co-curricular programs? From this study, four major findings emerged: students are dealing with advisers and hostile STEM classroom environments, they find community in their STEM enrichment environment, they feel validated and comfortable in their STEM co-curricular environments, and they are supported academically and professionally within their co-curricular STEM environments. These phenomena were prevalent for women in STEM peer-based and research programs from a variety of academic majors. The significance of this study is to inform institutional administrators and practitioners of the experiences and perspectives of some of their most vulnerable and underrepresented students.). Their perception of support within STEM enrichment programs are needed to facilitate enhancements for their student experiences. The study can also inform future research for studying and centering the experiences of Black women in STEM, enhancing institutional policies and practices to support Black women STEM students in the classroom and in cocurricular environments. [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.]