As the fastest growing minority serving institution type, Hispanic-serving institutions (HSIs) play important roles in reaching and serving a diverse group of students beyond Hispanic/Latine-identified students, including Black students. To understand Black STEM transfer students' experiences at an HSI, we conducted and analyzed 10 student interviews guided by Harris and Wood's Socio-Ecological Outcomes model. We found four themes. The first theme revealed participants had positive impressions of the HSI before transfer, due to its perceived racial/ethnic diversity. The second and third themes pointed to negative experiences after participants' arrival at the HSI, connected to their status as transfer students and as Black students, respectively. In the final theme, participants exercised their agency, which allowed them to persist and succeed despite inadequate institutional support. Based on these findings, we urge HSIs to intentionally devote more attention and resources to support Black STEM transfer students and otherwise minoritized students.