This presentation explores the impact of a STEM Preprofessional Workshop Series (STEM PPWS) at Morgan State University, a Historically Black College and University (HBCU), aimed at enhancing the career readiness and professional development of underrepresented minority (URM) students in STEM. Data from three cohorts over three academic years show significant increases in students' STEM self-efficacy, persistence, and career aspirations, as well as improved graduate school readiness. These findings demonstrate the effectiveness of targeted professional development initiatives at HBCUs in advancing URM success and fostering diversity in STEM fields.