Individuals in some racial or ethnic groups are less likely to receive federal funding from Mentored K career development award. The authors of this study seeks to indentify variables that explain the association between race/ethnicity and mentored K award receipt. Research-related activities during/after medical school and standardized academic measures largely explained the association between race/ethnicity and mentored K award in this national cohort. Interventions targeting these mediators could mitigate racial/ethnic disparities in the federally funded physician-scientist research workforce.