We explored the association between neighborhood residential racial composition and breast cancer mortality among Black and White breast cancer patients in Georgia and whether spatial access to cancer care mediates this association. Participants included 15,256 women living in 15 metropolitan statistical areas in Georgia who were diagnosed with breast cancer between 1999 and 2003. Residential racial composition was operationalized as the percent of Black residents in the census tract. We used gravity-based modeling methods to ascertain spatial access to oncology care. Multilevel Cox proportional hazards models and mediation analyses were used to test associations. Black women were 1.5 times more likely to die from breast cancer than White women. Residential racial composition had a small but significant association with breast cancer mortality (hazard ratios [HRs] = 1.04-1.08 per 10% increase in the percent of Black tract residents). Individual race did not moderate this relationship, and spatial access to care did not mediate it. Residential racial composition may be part of the socioenvironmental milieu that produces increased breast cancer mortality among Black women. However, there is a lack of evidence that spatial access to oncology care mediates these processes.