Historically Black colleges and universities (HBCUs) are noted for their success in broadening participation in science, technology, engineering, and mathematics (STEM). A multiple case study approach was used to identify institutional and leadership characteristics that may drive the success of small HBCUs in broadening participation in STEM. Data on 15 HBCUs were obtained from websites, including institutional websites, and the Integrated Postsecondary Education Data System (IPEDS). Factors common to many institutions included external STEM education funding, STEM-/research-focused missions, commitment of leaders to STEM education, partnerships to support STEM education, STEM faculty professional development, and STEM student support strategies. These characteristics also predicted the percentage of STEM graduates. Implications for future research include illuminating the pathways by which institutional and leadership factors influence student outcomes.