Background: Clinical trials are essential for developing novel cancer treatments and improving survival. However, Black women with breast cancer have higher cancer mortality rates compared to non-Black women and are less likely to be enrolled in clinical trials. This study aimed to understand barriers and facilitators to clinical trial participation among Black women with breast cancer to inform the design of a mobile health application (app). Methods: Semi-structured interviews lasting 45-60 minutes were conducted between May and September 2022 with a purposive sample of 20 Black women with breast cancer receiving care in academic and community practices in North Carolina. Participants were asked open-ended questions about their perspective on clinical trial participation. Interviews were digitally recorded, transcribed, and analyzed following a consensus coding-based thematic analysis. Results: Participants represented various age groups ranging from 33 to 76 years, breast cancer hormone receptor/HER 2 status, and stage. Several themes related to facilitators and barriers to clinical trial participation emerged from the interviews. Facilitators included prior experience with participating in clinical trials (cancer treatment, behavioral, and symptom management trials); desire to increase representation of Black women in cancer research to better understand how treatments may affect them differently; benefitting others; and potential for less intensive treatment regimens. Barriers included concern with adverse health effects; fear of new drugs and uncertain therapeutic effect; historical exploitation of Black people participating in research and medical care; lack of representation of Black people participating in clinical research; lack of clinical trial opportunities; concern with the term “trial” and being treated as a guinea pig; and concern with getting a placebo. Most participants were willing to use a mobile health app to obtain trusted information about clinical trials. Recommended content for the app included clinical trial risks and benefits, personal testimonials, link to available clinical trials, and resources to address logistical barriers such as transportation. Most participants also reported the importance of having Black people represented in their healthcare team and health messaging to improve trust in clinical trials. Conclusions: Several barriers and facilitators to clinical trial participation were identified. These findings will inform the content of a mobile health app designed to improve engagement of Black women with breast cancer in clinical trial discussions. Presence of racially representative clinicians and research staff was also noted to improve participation of Black women with breast cancer in clinical trials.